sos: remove vdsm pki private keys collection

Change-Id: Iae8371de3c415c946608c2192315cf2f219da630
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1162784
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/35241
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>