Database: Cast to int in estimateRowCount(), selectRowCount()

Database: Cast to int in estimateRowCount(), selectRowCount()

Doc comments state that these methods return ints. In order to ensure
that, values must be cast to int before they are returned.

With respect to selectRowCount(), follows-up 65f81d284386.

Change-Id: I108221ce4ad1b5b103b015fe875de54e04781741