deploy: Add `ADMIN_BASE_URL` in Admin conf

Add an `ADMIN_BASE_URL` setting in the admin.conf file. The value of
this setting is created in the same fashion as the values for
CYCLADES_BASE_URL / ASTAKOS_BASE_URL.

snf-deploy/files/etc/synnefo/admin.conf

-## Uncomment the following line when admin is installed in a separate node.
-## This setting cuts all other urls and uses only the urls of admin.
-#ROOT_URLCONF="synnefo_admin.admin.urls"
+ADMIN_BASE_URL = 'https://%ADMIN%/admin'

snf-deploy/snfdeploy/components.py

@@ -1569,8 +1569,11 @@ class Admin(base.Component):
         return []
 
     def _configure(self):
+        r1 = {
+            "ADMIN": self.ctx.admin.cname,
+        }
         return [
-            ("/etc/synnefo/admin.conf", {}, {})
+            ("/etc/synnefo/admin.conf", r1, {})
             ]
 
     @base.run_cmds