Couchbase server doesn't handle wall-clock time changes

Steps to reproduce:

• set up single node cluster
• set time 2 hours back
• load data in membase
• observe that nothing is getting persisted to disk
• set time 2 hours forward
• observe that is started persisting data

Accoring to Dustin, ep-engine's dispatcher uses pthread_cond_timedwait which uses absolute value of wall-clock time. POSIX allows to configure waiting using monotonic clock, but that feature is optional.

The proposal for now is to avoid large wall-clock changes. Users should run ntpd to keep node's time in sync, but membase service should be started after initial clock synchronization is done.