CBIDXT-83 Improve Timekeeper to track TS flush progress
CBIDXT-83 Improve Timekeeper to track TS flush progress

Timekeeper now keeps track of TS flush for a bucket. A new stability TS
is sent only when the previous flush for the bucket is done. Otherwise,
it gets queued up.

Change-Id: Id4dbd7bf938ea87c72a3c5bcbfa9073a1cb76971
Reviewed-on: http://review.couchbase.org/38865
Reviewed-by: Pratap Chakravarthy <3f7aa3c5f732447448ccfcd013fd9591a9825870@couchbase.com>
Reviewed-by: Deepkaran Salooja <94315e58ef7caa1d9829288fe30465d5fa6ccd83@gmail.com>
Tested-by: Deepkaran Salooja <94315e58ef7caa1d9829288fe30465d5fa6ccd83@gmail.com>

t3rm1n4l/indexing,t3rm1n4l/indexing,jchris/indexing,jchris/indexing,jchris/indexing,jchris/indexing