TT#55162 Fix system-tests accordingly to the current defaults

See the long description in commit 92dccb4b106d56c to ngcpcfg.git.

Change-Id: Ib6af6ab4471e9ab70142762a50bfd2a2c0e2ab4d

templates/130_filesys-ngcp.yaml.tt2

@@ -10,9 +10,9 @@ file:
 
   /etc/ngcp-config/config.yml:
     exists: true
-    mode: "0600"
+    mode: "0660"
     owner: root
-    group: root
+    group: _ngcp-admin
     filetype: file
     contains: []
 
@@ -26,9 +26,9 @@ file:
 
   /etc/ngcp-config/network.yml:
     exists: true
-    mode: "0644"
+    mode: "0660"
     owner: root
-    group: root
+    group: _ngcp-admin
     filetype: file
     contains: []