ocfs2: fix memory leak

Stanse found that o2hb_heartbeat_group_make_item leaks some memory on
fail paths. Fix the paths by adding a new label and jump there.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: ocfs2-devel@oss.oracle.com
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Joel Becker <joel.becker@oracle.com>