crl-storer: simplify S3 error handling (#6417)
crl-storer: simplify S3 error handling (#6417)

Currently, we refuse to error out when checking the error from
S3, to ensure that we can update the metrics appropriately. This
requires us to use an unconventional error-checking structure,
and to check the error again when it comes time to return.

Instead, move the metrics above the error check, and then make
the error check a more traditional structure.
letsencrypt/boulder,letsencrypt/boulder,letsencrypt/boulder