Fixes TestPullUpdates.shouldPullUpdatesOnStartupNoMatterWhat

Introduces a no op tx before checking for update pull on startup,
 since now the slave switching happens in a different thread and
 may time differently. This ensures that the read only assertion
 is covered by a check on the AvailabilityGuard.
Ignores BackupHaIT temporarily

The test fails because of known bugs that have already been solved in master.
 When those have been backported, the test must be reenabled.
Added purge monitoring to GCR cache

Pulled in Rickards Monitors utility for easier and collected monitoring of
components in the database.

Also, when purging will not purge the item at the the position where the
purge starts since that position will be the most recently put/updated
position so it doesn't make sense to directly purge it after put/update.