jbd2: fix incorrect unlock on j_list_lock

When 'jh->b_transaction == transaction' (asserted by below)

  J_ASSERT_JH(jh, (jh->b_transaction == transaction || ...

'journal->j_list_lock' will be incorrectly unlocked, since
the the lock is aquired only at the end of if / else-if
statements (missing the else case).

This bug has been introduced by an earlier change named
"jbd2: minimize region locked by j_list_lock in journal_get_create_access()".

Signed-off-by: Taesoo Kim <tsgatesv@gmail.com>

Index: linux-3.10.0-327.36.1.el7/fs/jbd2/transaction.c
===================================================================
--- linux-3.10.0-327.36.1.el7.orig/fs/jbd2/transaction.c
+++ linux-3.10.0-327.36.1.el7/fs/jbd2/transaction.c
@@ -1091,6 +1091,7 @@
 		JBUFFER_TRACE(jh, "file as BJ_Reserved");
 		spin_lock(&journal->j_list_lock);
 		__jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);
+		spin_unlock(&journal->j_list_lock);
 	} else if (jh->b_transaction == journal->j_committing_transaction) {
 		/* first access by this transaction */
 		jh->b_modified = 0;
@@ -1098,8 +1099,8 @@
 		JBUFFER_TRACE(jh, "set next transaction");
 		spin_lock(&journal->j_list_lock);
 		jh->b_next_transaction = transaction;
+		spin_unlock(&journal->j_list_lock);
 	}
-	spin_unlock(&journal->j_list_lock);
 	jbd_unlock_bh_state(bh);
 
 	/*