SPY-157: Fix auth logging times.

Motivation
----------
In the previous commit which added logging, it measured nanoseconds and printed
milliseconds. This also screwed up the debug/warn metric.

Modifications
-------------
Correctly convert nanoseconds to milliseconds.

Result
------
Timings are now properly warned and formatted.

Change-Id: Id174a49e03e052f9e32c98cc32aa7ad0b82bbb4d
Reviewed-on: http://review.couchbase.org/34936
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>