work around 'docker rm -f' weirdness

I've been seeing

~# docker rm -f weave
Error response from daemon: Cannot destroy container weave: Driver devicemapper failed to remove root filesystem 29e46c3e400ee3c8654f2b06a0f6d97bde98dfeb9bb61d25195dba38c04324fc: Device is Busy

whereas the corresponding two-step 'docker kill' + 'docker rm' works
fine.

weaver/weave

@@ -152,9 +152,10 @@ case "$COMMAND" in
         exit 0
         ;;
     stop)
-        if ! docker rm -f weave >/dev/null 2>&1 ; then
+        if ! docker kill weave >/dev/null 2>&1 ; then
             echo "Weave is not running."
         fi
+        docker rm -f weave >/dev/null 2>&1 || true
         if command_exists conntrack
         then
             conntrack -D -p udp --dport 6783 >/dev/null 2>&1