b2b entities/logic: Inherit db_default_url if possible

If there is still no DB URL, simply start without DB support (just as
before)

(cherry picked from commit ff7b584)
(cherry picked from commit a54424b)
(cherry picked from commit 0684e98)

modules/b2b_entities/b2b_entities.c

@@ -203,9 +203,12 @@ static int mod_init(void)
 		return -1;
 	}
 	memset(&b2be_dbf, 0, sizeof(db_func_t));
+
+	if(b2be_db_mode)
+		init_db_url(db_url, 1);
+
 	if(b2be_db_mode && db_url.s)
 	{
-		db_url.len = strlen(db_url.s);
 		b2be_dbtable.len = strlen(b2be_dbtable.s);
 
 		/* binding to database module  */

modules/b2b_logic/b2b_logic.c

@@ -248,9 +248,11 @@ static int mod_init(void)
 		return -1;
 	}
 
+	if(b2bl_db_mode)
+		init_db_url(db_url, 1);
+
 	if(b2bl_db_mode && db_url.s)
 	{
-		db_url.len = strlen(db_url.s);
 		b2bl_dbtable.len = strlen(b2bl_dbtable.s);
 		/* binding to database module  */
 		if (db_bind_mod(&db_url, &b2bl_dbf))