tool: fix pyflakes errors[1].

recently I broke master at change 31293.

[1]
./lib/vdsm/tool/configurators/libvirt.py:29: 'NotRootError' imported but unused
./lib/vdsm/tool/configurators/sanlock.py:24: 'NotRootError' imported but unused

Change-Id: I8e86dd38e3a871d55ffc5cb67d5f4596ec4dc3a6
Signed-off-by: Mooli Tayer <mtayer@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/32256
Reviewed-by: Dan Kenigsberg <danken@redhat.com>