ipacert: Revoking with removeFromCRL should be handled as cert release

When a revoked certificate with reason 6 (certificateHold) is revoked
with reason 8 (removeFromCRL), the effect is that the certificate is
valid again, as it is the same procedure as 'state: release'.

This is, at least, the behavior with IPA CLI comands, which is
implemented by this patch.

A new test is added to verify this behavior:

    tests/cert/test_cert_remove_hold_with_removeFromCRL.yml