pki: openssh: workaround rhel-6 keygen incompatibility
pki: openssh: workaround rhel-6 keygen incompatibility

Principals parameter differ in rhel-6.

Upstream/fedora/rhel-7:
    ssh-keygen -s ca_key -I certificate_identity [-h] [-n principals]
        [-O option] [-V validity_interval] [-z serial_number] file ...

rhel-6:
    ssh-keygen -s ca_key -I certificate_identity [-h] [-Z principals]
        [-O option] [-V validity_interval] [-z serial_number] file ...

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1235253
Change-Id: I372c4ad5760400f4875741f2b095e3234c7baac4
Signed-off-by: Alon Bar-Lev <2e3ceb4d37adc6ae3ccc00d3646e0e0a036ace03@redhat.com>

eayun/ovirt-engine,yapengsong/ovirt-engine,yingyun001/ovirt-engine,zerodengxinchao/ovirt-engine,eayun/ovirt-engine,yingyun001/ovirt-engine,zerodengxinchao/ovirt-engine,walteryang47/ovirt-engine,yapengsong/ovirt-engine,zerodengxinchao/ovirt-engine,yingyun001/ovirt-engine,eayun/ovirt-engine,zerodengxinchao/ovirt-engine,yapengsong/ovirt-engine,walteryang47/ovirt-engine,walteryang47/ovirt-engine,eayun/ovirt-engine,yingyun001/ovirt-engine,eayun/ovirt-engine,OpenUniversity/ovirt-engine,yingyun001/ovirt-engine,walteryang47/ovirt-engine,yapengsong/ovirt-engine,walteryang47/ovirt-engine,OpenUniversity/ovirt-engine,yapengsong/ovirt-engine,zerodengxinchao/ovirt-engine,OpenUniversity/ovirt-engine,OpenUniversity/ovirt-engine,OpenUniversity/ovirt-engine