Cleanup timeutils override in tests/functional/test_servers

The ServersTest._force_reclaim helper method sets up a timeutils
override but never removes it. This allows the override to potentially
leak into other tests causing spurious failures in completely unrelated
tests.

Change-Id: I637a1dd6301e5645a47dbd65026acfab83e6ae26
Closes-bug: 1399817
Merge "Cleanup timeutils override in tests/functional/test_servers"