MT#21583 MT#19009 kamailio: fix upgrade to 4.4.0

* active_watchers.user_agent had no default value

> [km_dbase.c:128]: db_mysql_submit_query(): driver error on query: Field 'user_agent' doesn't have a default value (1364)

Change-Id: Ie9e7091dbc6f4122056fddc01f514222f61f948e
(cherry picked from commit 71cfe4ee72)

db_scripts/diff/15264_not_replicated.up

@@ -0,0 +1,12 @@
+set sql_log_bin=0;
+set autocommit=0;
+
+START TRANSACTION;
+
+USE kamailio;
+
+-- table: active_watchers
+ALTER TABLE active_watchers
+  MODIFY COLUMN user_agent VARCHAR(255) DEFAULT '' NOT NULL;
+
+COMMIT;