Bootstrap stats

Track bootstrap events, reboostrap events and failed bootstrap events
Use requestcounter in clientsocket stats
Fix time convertion (Nano to micro) bug

Make the method accept nanoseconds to avoid unnecessary
convertion.
Minor changes as per the review
Test for monitoring interval

Ensure checking the interval before returning the histogram
Record op time on the async code path
Check monitoring interval before getting histogram

Make sure that that if the interval is expired you return
a reset histogram and not the stale one.
Separate sync and async operation times
Fixing NPE in during client pool shutdown