MB-11847: Set estimatedValueCount in loadKVPairs phase

- Otherwise, ep_warmup_estimated_value count would show
"unknown" after warmup completes in some scenarios.
- Also remove unused functions.

Change-Id: I2e2fedf58dcd49a6f572f830c4566b0d8946033b
Reviewed-on: http://review.couchbase.org/40200
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>