* Move nonce retry from jws to http
The error raised by an "invalid nonce" response never appeared
inside jws.go, but instead it was handled at http.go, so it makes
sense to move the retry logic to that file. The previous code from
jws.go had no effect and did not solve issues related to invalid
nonces.
* Rename retry response variable name for clarity
* [reduce-locking] Prepare for change
* [reduce-locking] Do not lock on http request
* [reduce-locking] Move getNonce and getNonceFromResponse from jws struct cause they do not need access to it
* [reduce-locking] Extract nonceManager
* [reduce-locking] Add test that tries to show locking on http requests problem
* Close response body in error case
* Ensure the body of both responses is closed when polling for cert
Also make a new const of maxBodySize, and cap the number of polls
to a maximum of 1000.
* More correct placement for polling limit
* Move const to the top
Before read access to `nonces` field in jws structure (in `Nonces` method) was not synchronized and we were still able
to get `slice bounds out of range` panic when trying to "pop" value in `Nonces` method.
The race can be actually observed by running `Nonce` method multiple times in separate goroutines with th precondition is `len(jws.nonces) == 1`.
