Patch maas url with port addition

Change-Id: I763144f62553b01b4b4ba1b512c4323e7e94ad6c
Related-prod: PROD-30209
diff --git a/config-drive/master_config.yaml b/config-drive/master_config.yaml
index 80e2d13..dd5d1a4 100644
--- a/config-drive/master_config.yaml
+++ b/config-drive/master_config.yaml
@@ -31,6 +31,7 @@
 master_config:
   - &master_config |
     function _post_maas_cfg() {
+      sed -i 's/API_SERVER=.*/API_SERVER=localhost:5240/g' /var/lib/maas/.maas_login.sh
       source /var/lib/maas/.maas_login.sh
       # disable backports for maas enlist pkg repo. Those operation enforce maas
       # to re-create sources.list and drop [source] fetch-definition from it.