qemu-img: Fix leakage of options on error

Reported by Coverity.
Signed-off-by: NFam Zheng <famz@redhat.com>
Message-id: 20170515141014.25793-1-famz@redhat.com
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

qemu-img.c

@@ -295,6 +295,7 @@ static BlockBackend *img_open_opts(const char *optstr,
         if (qdict_haskey(options, BDRV_OPT_FORCE_SHARE)
             && !qdict_get_bool(options, BDRV_OPT_FORCE_SHARE)) {
             error_report("--force-share/-U conflicts with image options");
+            QDECREF(options);
             return NULL;
         }
         qdict_put(options, BDRV_OPT_FORCE_SHARE, qbool_from_bool(true));