tserver.wal.max.referenced needs a test

[keith-turner]

Is your feature request related to a problem? Please describe.

The functionality behind tserver.wal.max.referenced does not have a test.

Describe the solution you'd like

In an IT create many tables that each reference a single write ahead log by doing the following.

1. Lower the walog size to be really small
2. Create N tablets in a table
3. For each tablet write an amount of data that causes the walog to roll. This should cause N tablets to each reference a unique log
4. Assert that tablet minor compact because the tserver is referencing too many logs.