Extend debug logging

Add additional debug logs to provide more detailed information
about forwarded data between the primary and secondary instances:

- For each forwarding request sent from the primary
- For each event request received on the secondary
- For each index operation received on the secondary

A debug log already existed for cache eviction received on the
secondary instance.

Change-Id: I4ba720b38d64edb6a8967194e023c7b6e88a2b99
3 files changed