Increase default test timeout for timeout fixture

This commit increases the default timeout for a test specified in
.testr.conf from 250 secs to 500 secs. The default build timeout
used for waiting for resource deletion is 400 secs. By using a test
timeout that was smaller than the build timeout some slow async
resource creation and deletions weren't completing before the test
was marked as failed for taking to long

Change-Id: Ia6292e68a8c3a0a0c03667a15f528c2ec6a5fbed
Partial-Bug: #1218585
Merge "Increase default test timeout for timeout fixture"