LU-2190: Map ldd_params to ZFS dataset properties

At mkfs/tunefs/mount time the configuration utilities will access
a .ldd_params configuraton string.  This string consists of space
delimited key values pairs which must be saved somewhere.

For ldiskfs it makes sense to store this string on disk as part
of the binary lustre_disk_data structure.  But the logical place
for ZFS is to use the user dataset properties where all the other
lustre_disk_data fields are stored.

This patch updates the ZFS portions of the utilities to take the
.ldd_params string and break it apart in to individual key value
pairs which can be stored as user dataset properties.  This is
done by simply appending 'lustre:' to the provided param key.

The original .ldd_params field can then be reconstructed by
fetching all the dataset properties prefixed by 'lustre:' and
appending them with their keys.

The advantage in this approach is new parameters can be added
without the need to update utilties.

Change-Id: Ida1b0e845b27154b209cc807726ae6ed3d22d189
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
LU-2240 osd: change FID of /ROOT on zfs

Pre-production 2.4 code used FID_SEQ_LOCAL_FILE for /ROOT. With
ldiskfs that FID turns into IGIF which is mapped to MDT0 permanently.
With ZFS original local sequence, was used which makes existing setup
incompatibile with DNE. The intention of the patch is to fix this on
existing ZFS setups and replace FID with one from special FID_SEQ_ROOT
sequence which is mapped to MDT0 as well. For simplicity this is done
in few steps:

 - osd-zfs replaces direntry for /ROOT with the new FID and fixes OI
   so that the new FID is mapped to the same dnode
 - MDD finds all objects listed in /ROOT and updates linkEA properly
 - MDD removes ./.. which may be on disk for pre-production setups
 - finally MDD resets LMA on /ROOT with the new FID, which is later
   used to recognize already converted filesystems (or ones created
   with correct FID from the beginning) and skip this conversion code

Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Change-Id: I03062c6909146f9a3aed72f41c0708f9ef92bb82