app_queue: Fix multiple calls to a queue member that is in only one queue.

When ringinuse=no queue members can receive more than one call if these
calls happen at nearly the same time.

* Fix so a queue member does not receive more than one call from a queue.

NOTE: This fix does not prevent multiple calls to a member if the member
is in more than one queue.

* Did some refactoring to eliminate some code redundancy.

(issue ASTERISK-16115)
Reported by: nik600
Patches:
      jira_asterisk_16115_single_q_v1.8.patch (license #5621) patch uploaded by rmudgett
      Modified


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/1.8@378663 f38db490-d61c-443f-a65b-d21fe96a405b