Remove non-existent default pki_cert_chain_path
In the future pkispawn will validate all path params so the
default value for pki_cert_chain_path needs to be removed
since it points to a non-existent file. When the param is
actually used (e.g. for installing with an external CA)
CAInstance.__spawn_instance() will configure the param to
point to the actual cert chain.
Signed-off-by: Endi Sukma Dewata <edewata@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>