cdr / cel: Use event time at event creation instead of processing.

cdr / cel: Use event time at event creation instead of processing.

When updating times on CDR or CEL records using the time at which
it is done can result in times being incorrect if the system is
heavily loaded and stasis message processing is delayed.

This change instead makes it so CDR and CEL use the time at which
the stasis messages that drive the systems are created. This allows
them to be backed up while still producing correct records.

ASTERISK-28498

Change-Id: I6829227e67aefa318efe5e183a94d4a1b4e8500a