Move all the cgroup data into separate files out of vircgroupmock.c
and rework the fopen function to load data from files.  This will
make it easier to add more test cases.
Reviewed-by: NFabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>