block: Fix update of BDRV_O_AUTO_RDONLY in update_flags_from_options()

Commit e35bdc12 added the auto-read-only option and the
code to update its corresponding flag in update_flags_from_options(),
but forgot to clear the flag if auto-read-only is false.
Signed-off-by: NAlberto Garcia <berto@igalia.com>
Reported-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block.c

@@ -1137,7 +1137,7 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags)
 
 static void update_flags_from_options(int *flags, QemuOpts *opts)
 {
-    *flags &= ~BDRV_O_CACHE_MASK;
+    *flags &= ~(BDRV_O_CACHE_MASK | BDRV_O_RDWR | BDRV_O_AUTO_RDONLY);
 
     assert(qemu_opt_find(opts, BDRV_OPT_CACHE_NO_FLUSH));
     if (qemu_opt_get_bool_del(opts, BDRV_OPT_CACHE_NO_FLUSH, false)) {
@@ -1149,8 +1149,6 @@ static void update_flags_from_options(int *flags, QemuOpts *opts)
         *flags |= BDRV_O_NOCACHE;
     }
 
-    *flags &= ~BDRV_O_RDWR;
-
     assert(qemu_opt_find(opts, BDRV_OPT_READ_ONLY));
     if (!qemu_opt_get_bool_del(opts, BDRV_OPT_READ_ONLY, false)) {
         *flags |= BDRV_O_RDWR;