[PATCH] nfsd: clear signals before exiting the nfsd() thread

Fixes the error "RPC: failed to contact portmap (errno -512)." when the server
later tries to unregister from the portmapper.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>