rgw: make some logging easier to read

rgw: make some logging easier to read

While __PRETTY_FUNCTION__ includes more information, it can clutter
the logs. So this reverts some uses of __PRETTY_FUNCTION__ back to
__func__.

I'm thinking that a strategy going forward is for the function entry
logging to use __PRETTY_FUNCTION__ to disambiguate overloaded
functions, but all others in the function simply to use __func__.

Signed-off-by: J. Eric Ivancich <ivancich@redhat.com>