MEDIUM: ssl: temporarily load files by detecting their presence in crt-store

MEDIUM: ssl: temporarily load files by detecting their presence in crt-store

crt-store is maint to be stricter than your common crt argument on a
bind line, and is supposed to be a declarative format.

However, since the 'ocsp-update' was migrated from ssl_conf to
ckch_conf, the .issuer file is not autodetected anymore when adding a
ocsp-update keyword in a crt-list file, which breaks retro-compatibility.

This patch is a quick fix that will disappear once we are able to be
strict on a crt-store and autodetect on a crt-list.