autofs: fix a leak in autofs_expire_indirect()

if the second call of should_expire() in there ends up
grabbing and returning a new reference to dentry, we need
to drop it before continuing.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/autofs/expire.c

@@ -459,9 +459,10 @@ static struct dentry *autofs_expire_indirect(struct super_block *sb,
 		 */
 		how &= ~AUTOFS_EXP_LEAVES;
 		found = should_expire(expired, mnt, timeout, how);
-		if (!found || found != expired)
-			/* Something has changed, continue */
+		if (found != expired) { // something has changed, continue
+			dput(found);
 			goto next;
+		}
 
 		if (expired != dentry)
 			dput(dentry);