ocfs2: Check heartbeat mode for kernel stacks only

commit 52c303c56c3638944b5f733e3961dc58eb8c7270 upstream.

Commit 2c442719e90a44a6982c033d69df4aae4b167cfa added some checks for proper
heartbeat mode when the o2cb stack is running.  Unfortunately, it didn't
take into account that a userpsace stack could be running. Fix this by only
doing the check if o2cb is in use. This patch allows userspace stacks to
mount the fs again.

Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>