Since 11c14bd2f5 CA certificates referenced in ca sections were
enumerated by two credential sets if they were also stored in
ipsec.d/cacerts. This caused duplicate certificate requests to
get sent. All CA certificates, whether loaded automatically or
via a ca section, are now stored in stroke_ca_t.
Certificates referenced in ca sections are now also reloaded
when `ipsec rereadcacerts` is used.