Update two low level traversal counter taps, adding a third to be
consistent with each other, and the other tap names in the system.
Update the AbstractStore tap name.
Remove the scan_abandons tap
Remove dead code
merge tjoneslo: Traverse taps update

Merge pull request #1283 from tjoneslo/sql-layer/traverse-taps-update
https://github.com/FoundationDB/sql-layer/pull/1283