common/rc: report kmemleak errors

common/rc: report kmemleak errors

If kmemleak is enabled, scan and report memory leaks after every
test.

Note that the kmemleak check support is EXPERIMENTAL! Due to the way
kmemleak works, the leak might be from an earlier test, or something
totally unrelated.

[eguan: add EXPERIMENTAL disclaimer in commit log too]

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>