Support masking the WRITE_SYNC latency from ChronologyProtector

• Use OutputPage::output() as the method to mask latency, since it takes a good while to run. By the time it runs, cache replication should have caught up, so the reap call will likely not block.
• For redirects emitted after changes in POST, instead of masking with OutputPage, add a parameter to the redirect and block on the positions appearing. This uses the redirection RTT to mask the replication latency.

Change-Id: Ib23690c302e8033610fef9a0ef451dafe8a5803e