lockd: dont return EAGAIN for a permanent error

Fix nlm_fopen() to return NLM_FAILED (or NLM_LCK_DENIED_NOLOCKS) instead
of NLM_LCK_DENIED.  The latter means the lock request failed because of a
conflicting lock (i.e.  a temporary error), which is wrong in this case.

Also fix the client to return ENOLCK instead of EAGAIN if a blocking lock
request returns with NLM_LOCK_DENIED.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: David Teigland <teigland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>