Better use of UTC-based timing

[rickb777]

This is based on source code inspection of logging/logging.go.

Lines 59-61 get the time in the local timezone.

start := al.clock()
al.handler.ServeHTTP(wrapper, r)
end := al.clock()

Line 87 does a conversion to UTC

start.In(time.UTC).Format(apacheFormat),

and line 95 is

end.Sub(start).Nanoseconds()/int64(time.Millisecond)

There is a rare problem that the duration calculation will be in error when daylight saving turns on or off, for locales that have it. A simple solution might be to change lines 59 and 61

start := al.clock().UTC()
al.handler.ServeHTTP(wrapper, r)
end := al.clock().UTC()

and simplify line 87

start.Format(apacheFormat),