srdb1 Check if the module is loaded, so the error message makes sense…

… in case of missing module

If a module use a default database and it's not loaded, currently
Kamailio complains that the module doesn't implement an API function
instead of actually telling the Kamailian that the module is not loaded.
This patch modifies that behaviour.

(cherry picked from commit c1a1a1b)
(cherry picked from commit 7e788aa)

lib/srdb1/db.c

@@ -207,6 +207,10 @@ int db_bind_mod(const str* mod, db_func_t* mydbf)
 		tmp = name;
 	}
 
+	if (!find_module_by_name(tmp)) {
+		LM_ERR("Module %s not found. Missing loadmodule? \n", tmp);
+		goto error;
+	}
 	dbind = (db_bind_api_f)find_mod_export(tmp, "db_bind_api", 0, 0);
 	if(dbind != NULL)
 	{