CI: Update buildAsterisk.sh to do a "make full"

If you do a "make all" when building Asterisk the xml documentation
produced will be missing certain AMI events where their
documentation is located not at the top of the c source file but
embedded further down next to the event's manager_event()
registration call.  See main/manager_mwi.c for an example.

"make full" does produce the correct documentation so we're changing
it in the build script.  A separate commit/issue will address the
problem with "make all".

ASTERISK-28507
Reported by: David Lee

Change-Id: I4a22635d6eef99eacecc0efb69e28360eebdb86c