Add bash completion for `--storage-opt dm.libdm_log_level`

This adds bash completion for https://github.com/moby/moby/pull/33845.

Signed-off-by: Harald Albers <github@albersweb.de>

contrib/completion/bash/docker

@@ -2068,6 +2068,10 @@ _docker_daemon() {
 			COMPREPLY=( $( compgen -W "ext4 xfs" -- "${cur##*=}" ) )
 			return
 			;;
+		dm.libdm_log_level)
+			COMPREPLY=( $( compgen -W "2 3 4 5 6 7" -- "${cur##*=}" ) )
+			return
+			;;
  	esac
 
 	case "$prev" in
@@ -2109,6 +2113,7 @@ _docker_daemon() {
 				dm.blocksize
 				dm.directlvm_device
 				dm.fs
+				dm.libdm_log_level
 				dm.loopdatasize
 				dm.loopmetadatasize
 				dm.min_free_space