skel: fix regression in alarms properties affecting dcache database commands

The elimination of scoping and db.* properties did not take into account the ability to run turn the alarm service off or to use xml.

Specifically, when alarms.db.type is not 'rdbms' dcache database ls should not report the presence of the alarm database, and more importantly, dcache database update should not attempt to run the liquibase changesets (since there may be no rdbms alarm database present at all).

This patch restores the correct behavior.

Testing done:

checked the database commands for correct behavior with alarms.db.type set to off, xml and rdbms.

Target: master
Require-notes: yes
Require-book: no
Acked-by: Paul

RELEASE NOTES:

If overriding the database name for alarms, be aware that alarms.db.type will not affect the dcache database commands; in particular, update will still attempt to run liquibase.  Thus any non-default setting for this property will require the actual presence of a database by that name.  Renaming is only relevant in the 'rdbms' case.