AGI: Only defer frames when in an interception routine.

AGI recently was modified to defer important frames. This was because
when AGI was used in a connected line interception routine, the
resulting connected line frame would end up getting discarded by the
AGI.

However, this caused bad behavior in other cases. Specifically, during a
transfer, if someone attempted to manually set the Caller ID on a
channel in an AGI, the deferred connected line frame would end up
overwriting what had been manually set in the AGI.

Since the initial issue was specific to interception routines, this
change removes the manual frame deferral from AGI and instead uses the
new frame deferral API in interception routines.

ASTERISK-26343 #close
Reported by Morton Tryfoss

Change-Id: Iab7d39436d0ee99bfe32ad55ef91e9bd88db4208