sosreport: remove Base class

Use of Base class inheritance breaks with sos>=3.1

Change-Id: I44816fdfe3197d655dda905c73a50e7c398b2e44
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1167828
Signed-off-by: Yeela Kaplan <ykaplan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/35759
Reviewed-by: Sandro Bonazzola <sbonazzo@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>