TLS connections will almost always create background connections to
perform cross-signed certificate downloads and OCSP checks.  There is
currently no direct visibility into which checks are taking place,
which makes troubleshooting difficult in the absence of either a
packet capture or a debug build.

Use the job progress message buffer to report the current cross-signed
certificate download or OCSP status check, where applicable.

Signed-off-by: Michael Brown <mcb30@ipxe.org>