nfsd: move fsnotify on client creation outside spinlock

This was causing a "sleeping function called from invalid context"
warning.

I don't think we need the set_and_test_bit() here; clients move from
unconfirmed to confirmed only once, under the client_lock.

The (conf == unconf) is a way to check whether we're in that confirming
case, hopefully that's not too obscure.

Fixes: 472d155a "nfsd: report client confirmation status in "info" file"
Signed-off-by: J. Bruce Fields <bfields@redhat.com>