Remove the list_servers_since_test

This test is mostly just a very good way to add new failures. There
are subtleties on the timestamping of servers which means that this
can often return the wrong number of servers. Because of this we
should just delete the test.

If we want something like this we should create a much more sane setup
that includes getting all the servers, determinging some subset that
the filter should return, fetching those, and getting the count.

Change-Id: I5c08ef031043229b76a6800eeaab6d418fc4614f
Merge "Remove the list_servers_since_test"