Removed defaultAccessList and fixed a couple of bugs

* draftAccessList is optional (and in some cases an error) with rev30
* Fixed credential expiration bug
* Fixed edge case where layer processing fails as already done
You can swap these to remove the nested if statement, which improves code readability.

if (credential.getExpiresInSeconds() > 0) {
  return credential;
}
if (credential.refreshToken()) {
  return credential;
}

...