xpp: dahdi_registration: force re-assignment

* The system state causing the bug:
  - DAHDI has auto_assign_spans==1
  - No /etc/dahdi/assigned-spans.conf

* The bug scenario:
  - During initial device detection, they are assigned by
    DAHDI driver.
  - Later we run "dahdi_span_assignment remove"
  - Then, a "dahdi_registration on" would not assign any span.

* The fix:
  - Using the '-R' option, force "dahdi_registration on" to also
    do "dahdi_span_assignment auto" on relevant devices.
  - This is the way it's called by /usr/share/dahdi/dahdi_auto_assign_compat

Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
Acked-by: Shaun Ruffell <sruffell@digium.com>
xpp: waitfor_xpds: handle missing serial numbers

Fixes a regression since 949ea4ca9f9c9050811af9e80d44530beb10fd8f
(2.7.0) - allows using an Astribank with no serial.

* Some of the olderst Astribanks don't have a serial number burned in
  them. Thus there is no serial attribute for the sysfs USB device node.

* waitfor_xpds identifies the Astribanks by their serial numbers.

* An lone Astribank without serial number would thus block waitfor_xpds
  (until timeout).

* Now we warn about them.

* We also try to handle it gracefully. As long as there's only one
  of thease, it would be counted as "NO-SERIAL".

Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
dahdi_genconf: remove hard-coded E1 default

* The "spantypes" generator had E1 default if no 'line-mode' parameter
  was passed.

* As a result the new logic in "dahdi_span_types dumpconfig" had no
  effect when called from dahdi_genconf, as it was always called
  with "--line-mode=" argument.

* Now "dahdi_genconf spantype" behaves just like
  "dahdi_span_types dumpconfig":
  - The "--line-mode=" forces generation of provided line-mode (E1/J1/T1)
  - Without this option, the generated config matches the current spans
    state according to new dahd_span_types default logic:
    - Wildcard rule if all spans have same line-mode.
    - Uncommented specific matches if spans have different line-modes.

Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
Acked-by: Russ Meyerriecks <rmeyerriecks@digium.com>