block: Fix -incoming with snapshot=on

The BDRV_O_INACTIVE flag should only be set for images explicitly opened
by the user. snapshot=on needs to create a new qcow2 image and write
some metadata to it. This is not a problem because it can't come from
the source, so there's no reason to mark it as BDRV_O_INACTIVE, even
though it is opened while waiting for the migration to complete.

This fixes an assertion failure when -incoming and snapshot=on are
combined.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -1191,10 +1191,6 @@ static int bdrv_fill_options(QDict **options, const char *filename,
         }
     }
 
-    if (runstate_check(RUN_STATE_INMIGRATE)) {
-        *flags |= BDRV_O_INACTIVE;
-    }
-
     return 0;
 }