slightly less early quorum

The early quorum change has maybe added a little bit too much
eventual to the consistency of requests in Swift, and users can
sometimes get unexpected
results.

This change gives us a knob to turn in finding the right balance,
by adding a timeout where pending requests can finish after quorum
is achieved.

Change-Id: Ife91aaa8653e75b01313bbcf19072181739e932c
Merge "slightly less early quorum"