TT#104760 Fix non-master admin privileges managing in API

* Forbid non-master admin to change own is_master,
	    read_only, and is_acitve flags; we have this logic
	    in old UI already in place

Change-Id: I81ab266d942e32dfb560ba488e9fd471ebc923f4
(cherry picked from commit b79d68e865)

lib/NGCP/Panel/Role/API/Admins.pm

@@ -140,6 +140,12 @@ sub update_item {
         resource => $resource,
     );
 
+    if($item->id == $c->user->id) {
+        # don't allow to take away own master rights/write permission, otherwise he'll not be
+        # able to manage any more admins
+        delete $resource->{$_} for qw(is_master is_active read_only);
+    }
+
     my $pass = $resource->{password};
     delete $resource->{password};
     if(defined $pass && $pass ne $old_resource->{saltedpass}) {