main/bridge_channel: Fix channel reference leak on video source

When a channel is made the video source, the bridge holds a reference to
it. Whenever the video source changes, that reference is released.
However, a ref leak does occur if the channel leaves the bridge (such as
being hung up) while it is the video source, as the bridge never
releases the ref in such a case.

This patch adds a line to the bridge_channel_internal_join routine such
that, when a channel finishes its time in the bridge, it notifies the
bridge via ast_bridge_remove_video_src that if it is a video source its
reference should be released.

ASTERISK-26555 #close

Change-Id: I3a2f5238a9d2fc49c591f0e65199d782ab0be76a

main/bridge_channel.c

@@ -2770,6 +2770,9 @@ int bridge_channel_internal_join(struct ast_bridge_channel *bridge_channel)
 	bridge_channel_settle_owed_events(bridge_channel->bridge, bridge_channel);
 	bridge_reconfigured(bridge_channel->bridge, 1);
 
+	/* Remove ourselves if we are the video source */
+	ast_bridge_remove_video_src(bridge_channel->bridge, bridge_channel->chan);
+
 	ast_bridge_unlock(bridge_channel->bridge);
 
 	/* Must release any swap ref after unlocking the bridge. */