vdsm: pki: fix permission of spice directory

old vdsm-bootstrap implementations touched
spice pki directory explicitly, so we need to revert
to something sane.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1008328
Change-Id: Ib47feea4d9beace8acc38cfc0e4cd18a46c22654
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>