Add logging for NSX status sync cache

This patch simply adds some log statements with debug
severity for tracking events related to the NSX object
cache kept by the operational status synchronization
thread.

This will  be helpful when debugging error conditions.

Change-Id: Ieb7b44b1117048c126d275dea2b8503b85eaba04
Related-Bug: 1329560
Merge "Add logging for NSX status sync cache"