Fix Segfault In app_queue When "persistentmembers" Is Enabled And Using Realtime

When the "ignorebusy" setting was deprecated, we added some code to allow us to
be compatible with older setups that are still using the "ignorebusy" setting
instead of "ringinuse".  We set a char *variable with the column name to use,
which helps the realtime functions to use the correct column in their SQL
queries.  When "persistentmembers" is enabled, we are not setting this variable
before the realtime functions were called to load members.  This results in the
variable being NULL and therefore causing a segfault when loading members during
the module's process of loading.

The solution was to move the code that sets that variable to be before these
realtime functions are called during the loading of the module.

(closes issue ASTERISK-21738)
Reported by: JoshE
Tested by: JoshE
Patches:
    asterisk-21738-rt-ringinuse-field-not-set.diff
                                     uploaded by Michael L. Young (license 5026)

Review: https://reviewboard.asterisk.org/r/2499/
........

Merged revisions 388108 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@388110 f38db490-d61c-443f-a65b-d21fe96a405b