Merge remote-tracking branch 'couchbase/3.0.x' into sherlock

Merge remote-tracking branch 'couchbase/3.0.x' into sherlock

* commit 'a430629':
  MB-19278: Fix lock-order inversion on ActiveStream::streamMutex
  MB-19277: Set executorThread's waketime to atomic
  MB-19276: Fix data race on ExecutorThread::taskStart
  MB-19275: Address data race on a DCP stream's state
  MB-19273: Fix data race on PassiveStream::buffer.{bytes,items}
  MB-19260: Make cookie atomic to serialize set/get in ConnHandler
  MB-19259: Fix data race on DcpConsumer::backoffs
  MB-19258: Address data race with replicationThrottle parameters
  MB-19281: [BP] Add template class RelaxedAtomic<>
  MB-19257: Fix data race on ExecutorThread::now
  MB-19256: Address possible data race on VBCBAdaptor::currentvb

Further merge of mostly TSan fixes from 3.0.x into sherlock.

Change-Id: Ic88c446c4e09d669f7a4da7f8cb2f97c13d70ab7