Check the result of cert request in replica installer
    
    When running ipa-replica-install in domain-level 1, the installer
    requests the LDAP and HTTP certificates using certmonger but does
    not check the return code. The installer goes on and fails when
    restarting dirsrv.
    
    Fix: when certmonger was not able to request the certificate, raise an
    exception and exit from the installer:
    
      [28/45]: retrieving DS Certificate
      [error] RuntimeError: Certificate issuance failed (CA_UNREACHABLE)
    Your system may be partly configured.
    Run /usr/sbin/ipa-server-install --uninstall to clean up.
    
    ipa.ipapython.install.cli.install_tool(CompatServerReplicaInstall): ERROR    Certificate issuance failed (CA_UNREACHABLE)
    ipa.ipapython.install.cli.install_tool(CompatServerReplicaInstall): ERROR    The ipa-replica-install command failed. See /var/log/ipareplica-install.log for more information
    
    https://fedorahosted.org/freeipa/ticket/6514
    
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>