qemu-img: Avoid setting ret to unused value in img_convert()

Coverity points out that we assign the return value from
bdrv_snapshot_load_tmp() to 'ret' in img_convert(), but then
never use that variable. (We check for failure by looking
at local_err instead.) Drop the unused assignment, bringing
the call into line with the following call to
bdrv_snapshot_laod_tmp_by_id_or_name().

(Fixes CID 1247240.)
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1486744104-15590-3-git-send-email-peter.maydell@linaro.org
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

qemu-img.c

@@ -1968,10 +1968,10 @@ static int img_convert(int argc, char **argv)
     }
 
     if (sn_opts) {
-        ret = bdrv_snapshot_load_tmp(bs[0],
-                                     qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
-                                     qemu_opt_get(sn_opts, SNAPSHOT_OPT_NAME),
-                                     &local_err);
+        bdrv_snapshot_load_tmp(bs[0],
+                               qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
+                               qemu_opt_get(sn_opts, SNAPSHOT_OPT_NAME),
+                               &local_err);
     } else if (snapshot_name != NULL) {
         if (bs_n > 1) {
             error_report("No support for concatenating multiple snapshot");