Bugfix: Timekeeper fix TS List management

- Timekeeper needs to remove stability TS from pending list
  once it sends that to indexer
- Use a separate copy of TS to send to indexer as the original
  copy keeps changing

Change-Id: I5d990a73e1bcb1320ede1d886d32e1d9f1747e40
Reviewed-on: http://review.couchbase.org/39081
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Tested-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>