Fix bash completion on systems where extglob is not set

Signed-off-by: Harald Albers <github@albersweb.de>
(cherry picked from commit 211e3b0df67d17989c7aff63d1a0098ad61f07a3)

contrib/completion/bash/docker

@@ -42,6 +42,9 @@
 # options immediately following their corresponding long form.
 # This order should be applied to lists, alternatives and code blocks.
 
+__docker_previous_extglob_setting=$(shopt -p extglob)
+shopt -s extglob
+
 __docker_q() {
 	docker ${host:+-H "$host"} ${config:+--config "$config"} 2>/dev/null "$@"
 }
@@ -1864,4 +1867,7 @@ _docker() {
 	return 0
 }
 
+eval "$__docker_previous_extglob_setting"
+unset __docker_previous_extglob_setting
+
 complete -F _docker docker