rbd: set TESTDIR when running xfstests

[elder@inktank.com: fixed typo]

Signed-off-by: Sage Weil <sage@inktank.com>
ceph.conf: debug ms = 1 for monitors

Signed-off-by: Sage Weil <sage@inktank.com>
exec, pexec: set TESTDIR

Signed-off-by: Sage Weil <sage@inktank.com>
rbd: drop udev

The packages have these rules now.

Signed-off-by: Sage Weil <sage@inktank.com>