Add zsh completion for 'docker {run,create} --volume-driver'

Signed-off-by: Steve Durrheimer <s.durrheimer@gmail.com>
(cherry picked from commit 8446a5c88bd744df7f7468ec7eb8d8dee4e7c7e9)
diff --git a/contrib/completion/zsh/_docker b/contrib/completion/zsh/_docker
index 0093049..c3076fc 100644
--- a/contrib/completion/zsh/_docker
+++ b/contrib/completion/zsh/_docker
@@ -334,7 +334,7 @@
         (create)
             _arguments \
                 $opts_help \
-                "($help -d --driver)"{-d,--driver=}"[Specify volume driver name]:Driver name: " \
+                "($help -d --driver)"{-d,--driver=}"[Specify volume driver name]:Driver name:(local)" \
                 "($help)--name=[Specify volume name]" \
                 "($help)*"{-o,--opt=}"[Set driver specific options]:Driver option: " && ret=0
             ;;
@@ -444,6 +444,7 @@
         "($help -t --tty)"{-t,--tty}"[Allocate a pseudo-tty]"
         "($help -u --user)"{-u,--user=}"[Username or UID]:user:_users"
         "($help)*-v[Bind mount a volume]:volume: "
+        "($help)--volume-driver=[Optional volume driver for the container]:volume driver:(local)"
         "($help)*--volumes-from=[Mount volumes from the specified container]:volume: "
         "($help -w --workdir)"{-w,--workdir=}"[Working directory inside the container]:directory:_directories"
     )