Do not leak Security::CertErrors created in X509_verify_cert() (#1346)

Do not leak Security::CertErrors created in X509_verify_cert() (#1346)

ACLFilledChecklist was using a raw C pointer for handling cbdata-managed
Security::CertErrors. Some sslErrors users knew about hidden cbdata
requirements, some did not, resulting in inconsistent locking/unlocking
and associated memory leaks. Upgrading ACLFilledChecklist::sslErrors to
smart CbcPointer fixes those leaks (and simplifies code).