Avoid quorum unavailable write.

Avoid the quorum unavailable write, which might succeed on one of the
nodes, triggering a transient failure in this test where the write
appears late and causes two subsequent reads to read two different
values.

This is an example of the partial write problem.
Merge pull request #65 from SyncFree/bugfix/csm/repfsm-partial-write

Avoid quorum unavailable write.