MT#3607 Fix create time for voip_subscribers

Older ngcp-panel versions didn't set the create_timestamp properly,
causing CSC to show a huge list of dates in the calls/vm view.

db_scripts/diff/15016.up

@@ -0,0 +1,4 @@
+USE provisioning;
+
+UPDATE voip_subscribers SET create_timestamp = '2013-01-01 00:00:00'
+  WHERE create_timestamp = '0000-00-00 00:00:00';