report: fix thin external snapshot identification for lv_layout and lv_type fields

Thin snapshots having external origins missed the "snapshot" keyword for
lv_type field. Also, thin external origins which are thin devices (from
another pool) were not recognized properly.

For example, external origin itself can be either non-thin volume (lvol0
below) or it can be a thin volume from another pool (lvol3 below):

Before this patch:

$ lvs -o name,vg_name,attr,pool_lv,origin,layout,type
  Internal error: Failed to properly detect layout and type for for LV vg/lvol3
  Internal error: Failed to properly detect layout and type for for LV vg/lvol3
  LV    VG     Attr       Pool  Origin Layout     Type
  lvol0 vg     ori-------              linear     external,origin,thin
  lvol2 vg     Vwi-a-tz-- pool  lvol0  thin       thin
  lvol3 vg     ori---tz-- pool         unknown    external,origin,thin,thin
  lvol4 vg     Vwi-a-tz-- pool1 lvol3  thin       thin
  pool  vg     twi-a-tz--              pool,thin  pool,thin
  pool1 vg     twi-a-tz--              pool,thin  pool,thin

- lvol2 as well as lvol4 have missing "snapshot" in type field
- lvol3 has unrecognized layout (should be "thin"), but has double
  "thin" in lv_type which is incorrect
- (also there's double "for" in the internal error message)

With this patch applied:

$ lvs -o name,vg_name,attr,pool_lv,origin,layout,type
  LV    VG     Attr       Pool  Origin Layout     Type
  lvol0 vg     ori-------              linear     external,origin,thin
  lvol2 vg     Vwi-a-tz-- pool  lvol0  thin       snapshot,thin
  lvol3 vg     ori---tz-- pool         thin       external,origin,thin
  lvol4 vg     Vwi-a-tz-- pool1 lvol3  thin       snapshot,thin
  pool  vg     twi-a-tz--              pool,thin  pool,thin
  pool1 vg     twi-a-tz--              pool,thin  pool,thin
report: also display "mirror" keyword in lv_type for pvmove LV and display "multiple" for external origin used for more than one thin snapshot

$ lvs -a -o name,vg_name,attr,layout,type
  LV        VG     Attr       Layout     Type
  lvol0     vg     -wI-a----- linear     linear
  [pvmove0] vg     p-C-aom--- mirror     mirror,pvmove

(added "mirror" for pvmove LV)

$ lvs -a -o name,vg_name,attr,layout,type
  LV              VG     Attr       Layout     Type
  lvol0           vg     ori------- linear     external,multiple,origin,thin
  [lvol1_pmspare] vg     ewi------- linear     metadata,pool,spare
  lvol2           vg     Vwi-a-tz-- thin       snapshot,thin
  lvol3           vg     Vwi-a-tz-- thin       snapshot,thin
  pool            vg     twi-a-tz-- pool,thin  pool,thin
  [pool_tdata]    vg     Twi-ao---- linear     data,pool,thin
  [pool_tmeta]    vg     ewi-ao---- linear     metadata,pool,thin

(added "multiple" for external origin used for more than one
thin snapshot - lvol0 in the example above)
report: also display "mirror" keyword in lv_layout for mirrored mirror log and "cache" keyword in lv_layout for cached cache pool

$ lvs -a -o name,vg_name,attr,layout,type
  LV                    VG     Attr       Layout     Type
  lvol0                 vg     mwi-a-m--- mirror     mirror
  [lvol0_mimage_0]      vg     iwi-aom--- linear     image,mirror
  [lvol0_mimage_1]      vg     iwi-aom--- linear     image,mirror
  [lvol0_mlog]          vg     mwi-aom--- mirror     log,mirror
  [lvol0_mlog_mimage_0] vg     iwi-aom--- linear     image,mirror
  [lvol0_mlog_mimage_1] vg     iwi-aom--- linear     image,mirror

(lvol0_mlog properly displayed as "mirror" layout for mirrored mirror log)

$ lvs -a -o name,vg_name,attr,layout,type
  LV                  VG     Attr       Layout     Type
  lvol0               vg     Cwi---C--- cache,pool cache,pool
  [lvol0_cdata]       vg     Cwi------- linear     cache,data,pool
  [lvol0_cmeta]       vg     ewi------- linear     cache,metadata,pool
  [lvol1_pmspare]     vg     ewi------- linear     metadata,pool,spare
  lvol2               vg     Cwi---C--- cache,pool cache,pool
  [lvol2_cdata]       vg     Cwi---C--- cache      cache,data,pool
  [lvol2_cdata_corig] vg     owi---C--- linear     cache,origin
  [lvol2_cmeta]       vg     ewi------- linear     cache,metadata,pool

(lvol2_cdata properly displayed as cached cache pool data)
lv: remove lv_type_name fn

The lv_type_name function is remnant from old code that reported
only single string for the LV type. LV types are now reported
in a more extended way as keyword list that describe the type
precisely (using lv_layout_and_type fn).

The lv_type_name was used in some error messages to display the
type of the LV so just reinstate the old messages back referencing
the type directly with a string - this is enough for error messages.
They don't need to display the LV type as precisely as it's used
on lvs output (which is optimized for selection anyway).
dmeventd: fix test for select return value

Do not call read when select return -1 && EINTR.
Also check for return valuer from read() and
abort write function when unexpected error happens.
metadata: check result of refresh and rescan

Detect failure in case refresh_filters of lvmcache_label_scan fails.
lvscan: check result of id_write_format

Currently rather impossible to happen - but check
for returned value of id_write_format().
lv_manip: check for str_list_dup failure
libdm: check version prints error

Move 'bad' label above log_error, so the
error message is printed on 'bad' path.
(And return 0 is not without log_error()).
cleanup: reindent and make obvious error path
cleanup: use _ prefix for static functions
cleanup: use just PATH_MAX size

Avoid playing with +1.

PATH_MAX code needs probably more thinking anyway, since
there is no MAX path in Linux - user may easily create path
with 64kB chars - so 4kB buffer is surelly not enough for
such dirs.

Note:
http://insanecoding.blogspot.cz/2007/11/pathmax-simply-isnt.html
cleanup: avoid double assign

Skip setting a value to a variable which is never
used and overwritten/set afterwards.
cleanup: simplier struct init

Use simplier struct initilizer.
cleanup: Remove extra ';' from the end of a line.
lvconvert: snapshot: allow using raid1 for snapshot and snapshot origin

When testing conversion sanity, we checked lv->status & MIRRORED
which encompasses both old mirrors and raid1 mirrors. But we need to
ban only the old mirrors here hence allow raid1 mirrors.
tests: proper /dev access

Commit 5ebff6cc9f631b7409d99b72fa0b39ccec30bf1f seemed to introduce
new 'for' loop but the mode is not yet used.
But the access to /dev dir needs to go through $DM_DEV_DIR
and whole path needs to be in "".
man: dmsetup: -n is shortcut for --notable, not --noheadings

The -n was defined for --notable since beginning, but the man page
got wrong at some time...
lvresize: Fix raid/mirror and %PE handling code.

Sort out the lvresize calculation code to handle size changes
specified as physical extents as well as logical extents
and to process mirror resizing and raid extensions correctly.

The 'approx alloc' option was masking the underlying problem.
lvcreate: disallow snapshot of cache lv