Add test for varz time_of_last_registry_update in router
Add test for varz time_of_last_registry_update in router

[#53722497]

ryan-talley/cf-bigip-ctlr,ryan-talley/cf-bigip-ctlr,ryan-talley/cf-bigip-ctlr,dramich/cf-bigip-ctlr,dramich/cf-bigip-ctlr,ryan-talley/cf-bigip-ctlr,dramich/cf-bigip-ctlr,dramich/cf-bigip-ctlr