Intermittent fail in test_document_expiry_values

The failure was not reproducible, but occurs at the comparison on line 480 of collection_t.py. This test really tries to do too much in a single test. Lets split it into multiple, simpler tests that individually test the 50 years vs 30 days, etc...

Also - possibly the issue comes down to how we get the expiry back from the server. When you ask the server to expire in 10 seconds, it makes it expire 10 seconds from when it was asked, according to the server's time, and I believe it rounds it up to the next second, rather than some 10 seconds from exactly now. This makes comparisons a bit tricky, you need a little range in those comparisons. The now and/or then variables are likely slightly problematic (note the +1 and -1).