block/mirror: drop extra error propagation in commit_active_start()

Let's check return value of mirror_start_job to check for failure
instead of local_err.

Rename ret to job, as ret is usually integer variable.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-Id: <20210202124956.63146-7-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

block/mirror.c

@@ -1860,8 +1860,7 @@ BlockJob *commit_active_start(const char *job_id, BlockDriverState *bs,
                               bool auto_complete, Error **errp)
 {
     bool base_read_only;
-    Error *local_err = NULL;
-    BlockJob *ret;
+    BlockJob *job;
 
     base_read_only = bdrv_is_read_only(base);
 
@@ -1871,19 +1870,18 @@ BlockJob *commit_active_start(const char *job_id, BlockDriverState *bs,
         }
     }
 
-    ret = mirror_start_job(
+    job = mirror_start_job(
                      job_id, bs, creation_flags, base, NULL, speed, 0, 0,
                      MIRROR_LEAVE_BACKING_CHAIN, false,
                      on_error, on_error, true, cb, opaque,
                      &commit_active_job_driver, false, base, auto_complete,
                      filter_node_name, false, MIRROR_COPY_MODE_BACKGROUND,
-                     &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
+                     errp);
+    if (!job) {
         goto error_restore_flags;
     }
 
-    return ret;
+    return job;
 
 error_restore_flags:
     /* ignore error and errp for bdrv_reopen, because we want to propagate