ipa-kra-install: fix pkispawn setting for pki_security_domain_hostname
    
    During ipa-kra-install, the installer prepares a configuration file
    provided to pkispawn. This configuration file defines
    pki_security_domain_hostname=(first master)
    
    but when we are installing a clone, it should be set to the local hostname
    instead, see man page pki_default.cfg:
          pki_security_domain_hostname, pki_security_domain_https_port
                  Location  of  the security domain.  Required for KRA, OCSP, TKS,
                  and TPS subsystems and for  CA  subsystems  joining  a  security
                  domain.  Defaults to the location of the CA subsystem within the
                  same instance.
    
    When pki_security_domain_hostname points to the 1st master, and this first
    master is decommissioned, ipa-kra-install fails on new replicas because pkispawn
    tries to connect to this (non-existing) host.
    
    https://pagure.io/freeipa/issue/6895
    
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>