If a writer continually asks to be reset then it should always succeed -
it should be the responsibility of the underlying content.Writer to
stop producing ErrReset after some amount of time and to instead return
the underlying issue - which pushWriter already does today, using the
doWithRetries function.
doWithRetries already has a separate cap for retries of 6 requests (5
retries after the original failure), and it seems like this would be
previously overridden by content.Copy's max number of 5 attempts, hiding
the original error.
Signed-off-by: Justin Chadwell <me@jedevc.com>