qa:  Add knfsd reexport suite

Feature http://tracker.newdream.net/issues/3621

Signed-off-by: David Zafman <david.zafman@inktank.com>
regression: include nfs suite
remove rbd_header_race test

This no longer works since export does not do a watch, and the race is
being closed a different way not detectable by this test.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>