cdr.c: Add container to key off of Party B channel names.

The CDR performance gets worse the further it gets behind in processing
stasis messages.  One of the reasons is because of a n*m loop used when
processing Party B information.

* Added a new CDR container that is keyed to Party B so we don't need such
a large loop when processing Party B information.

NOTE: To reduce the size of the patch I deferred to another patch the
renaming of the Party A active_cdrs_by_channel container to
active_cdrs_master and renaming the container's hash and cmp functions
appropriately.

ASTERISK-27335

Change-Id: I0bf66e8868f8adaa4b5dcf9e682e34951c350249