channel: Fix memory leak in suppress API.

A frame suppression API exists as part of channels
which allows audio frames to or from a channel to
be dropped. The MuteAudio AMI action uses this
API to perform its job.

This API uses a framehook to intercept flowing
audio and drop it when appropriate. It is the
responsibility of the framehook to free the
frame it is given if it changes the frame. The
suppression API failed to do this resulting in
a leak of audio frames.

This change adds the freeing of these frames.

ASTERISK-29071

Change-Id: Ie50acd454d672d36af914050c327d2e120d8ba7b