Fix a dead lock and remove some duplicated indications during un-hold

Fix a dead lock during un-hold procedure under race condition by
  * Remove duplicated indications for un-hold.
  * Narrow the usage of channel lock inside `chan_voicemngr_modify_codec
  * Remove the extra redirection for the case from: https://dev.iopsys.eu/voice/asterisk-chan-
    voicemngr/-/merge_requests/26 as it is not needed for now.

The dead lock is due to `ast_channel_get_by_name` used by `chan_voicemngr_modify_codec`(which
called during ssrc related indications) https://dev.iopsys.eu/voice/asterisk-chan-
voicemngr/-/blob/devel/src/channels/chan_voicemngr.c#L774 has a channel lock from
`ast_channel_by_name_cb`. And indications for different channels also have locks from
`ast_indicate_data`. They may waiting for each other during some massive indications between
bridged channels.


(cherry picked from commit 1e3a03a8)