Intermittent timeout of memcached_testapp tests in CV

The last test seemingly hits the time cap for running the tests (I assume this is 300s). This has been happening frequently with 15 instances in the last 100 CV runs of linux-master.

190/190 Test #116: memcached_testapp.default.TransportProtocols/DurabilityTest ..................***Timeout 300.09 sec

...

Total Test time (real) = 616.01 sec 

The following tests FAILED: 16:20:59 116 - memcached_testapp.default.TransportProtocols/DurabilityTest (Timeout)

In looking further into this issue, the test appear as 190/190 (or sometimes 2 so 189/190) as due to the time out they are the last to finish. However, it is not the 190th test as denoted in the example above by #116. This number varies but for linux-master it is currently commonly around the 117±20 range.

Now seen on both linux and windows cv machines

See comments for recent instances