Fix HDB two-phase commit for LDAP backend

We can't replay log entries when recovering if the backend is shared by
writers with separate logs (or no logs at all), i.e., on other hosts.

lib/hdb/hdb.h

@@ -71,6 +71,7 @@ enum hdb_lockop{ HDB_RLOCK, HDB_WLOCK };
 #define HDB_CAP_F_HANDLE_ENTERPRISE_PRINCIPAL 1
 #define HDB_CAP_F_HANDLE_PASSWORDS	2
 #define HDB_CAP_F_PASSWORD_UPDATE_KEYS	4
+#define HDB_CAP_F_SHARED_DIRECTORY      8
 
 /* auth status values */
 #define HDB_AUTH_SUCCESS		0