Cleanup after moving all zsh completion logics for the new image command

Signed-off-by: Steve Durrheimer <s.durrheimer@gmail.com>

contrib/completion/zsh/_docker

@@ -1984,7 +1984,7 @@ __docker_subcommand() {
         (attach|commit|cp|create|diff|exec|export|kill|logs|pause|unpause|port|rename|restart|rm|run|start|stats|stop|top|update|wait)
             __docker_container_subcommand && ret=0
             ;;
-        (build)
+        (build|history|import|load|pull|push|save|tag)
             __docker_image_subcommand && ret=0
             ;;
         (container)
@@ -2101,9 +2101,6 @@ __docker_subcommand() {
                 "($help)--until=[Events created until this timestamp]:timestamp: " \
                 "($help)--format=[Format the output using the given go template]:template: " && ret=0
             ;;
-        (history)
-            __docker_image_subcommand && ret=0
-            ;;
         (image)
             local curcontext="$curcontext" state
             _arguments $(__docker_arguments) \
@@ -2125,9 +2122,6 @@ __docker_subcommand() {
             words[1]='ls'
             __docker_image_subcommand && ret=0
             ;;
-        (import)
-            __docker_image_subcommand && ret=0
-            ;;
         (info|version)
             _arguments $(__docker_arguments) \
                 $opts_help \
@@ -2154,9 +2148,6 @@ __docker_subcommand() {
                     ;;
             esac
             ;;
-        (load)
-            __docker_image_subcommand && ret=0
-            ;;
         (login)
             _arguments $(__docker_arguments) \
                 $opts_help \
@@ -2224,19 +2215,10 @@ __docker_subcommand() {
             words[1]='ls'
             __docker_container_subcommand && ret=0
             ;;
-        (pull)
-            __docker_image_subcommand && ret=0
-            ;;
-        (push)
-            __docker_image_subcommand && ret=0
-            ;;
         (rmi)
             words[1]='rm'
             __docker_image_subcommand && ret=0
             ;;
-        (save)
-            __docker_image_subcommand && ret=0
-            ;;
         (search)
             _arguments $(__docker_arguments) \
                 $opts_help \
@@ -2285,9 +2267,6 @@ __docker_subcommand() {
                     ;;
             esac
             ;;
-        (tag)
-            __docker_image_subcommand && ret=0
-            ;;
         (volume)
             local curcontext="$curcontext" state
             _arguments $(__docker_arguments) \