Fix: duplicated kernel consumer socket locking

Commit 9d1103e introduced a bug causing a deadlock on snapshot record.
Function consumer_snapshot_channel is called with the lock held causing
the pthread_mutex_lock call inside to hang forever.

Because consumer_snapshot_channel now acquires the lock before using the
socket. No need to acquire the lock before calling the function.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>