Make interval a constant on proxy/config/etcd

Allow future testing of intervals
Remove long sleeps from proxy tests
dedupe registry.MakeEndpointController init
dedupe apiserver.New
Reduce nesting on ServiceRegistryStorage.Create
Merge pull request #773 from smarterclayton/speed_up_proxy_tests

Remove 8 seconds of unnecessary sleeps from proxy tests
ServiceRegistryStorage.Delete should respect zone.
Merge pull request #775 from nyaxt/misc_cleanup

Minor clean ups for readability
Merge pull request #776 from nyaxt/respectzone

ServiceRegistryStorage.Delete should respect zone.
Add a utility for doing master election via etcd.