fix tests in 'vzdump_new_test.pl'

commmit
b241deb7 ("close #3476: vzdump: add job-init hook")

introduces a 'cfs_update' in VZDump->new(), which overwrites our
carefully prepared storage/vm config which can break the tests

to prevent this, mock 'cfs_update' to do nothing, since we never
want to load the 'real' configs during tests anyway

fixes commit b241deb731

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

test/vzdump_new_test.pl

@@ -61,6 +61,10 @@ $pve_cluster_module->mock(
 	die "unexpected filename '$filename'\n" if $filename ne 'storage.cfg';
 	return $storage_config;
     },
+    # never update during the tests
+    cfs_update => sub {
+	return;
+    },
 );
 
 my $pve_tools_module = Test::MockModule->new('PVE::Tools');