tlscert: Don't force 'keyEncipherment' for ECDSA and ECDH

tlscert: Don't force 'keyEncipherment' for ECDSA and ECDH

Per RFC8813 [1] which amends RFC5580 [2] ECDSA, ECDH, and ECMQV
algorithms must not have 'keyEncipherment' present, but our code did
check it. Add exemption for known algorithms which don't use it.

[1] https://datatracker.ietf.org/doc/rfc8813/
[2] https://datatracker.ietf.org/doc/rfc5480

Closes: https://gitlab.com/libvirt/libvirt/-/issues/691
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>