nfsd4: fix leak of inode reference on delegation failure

commit bf7bd3e98be5c74813bee6ad496139fb0a011b3b upstream.

This fixes a regression from 68a33961
"nfsd4: shut down more of delegation earlier".

After that commit, nfs4_set_delegation() failures result in
nfs4_put_delegation being called, but nfs4_put_delegation doesn't free
the nfs4_file that has already been set by alloc_init_deleg().

This can result in an oops on later unmounting the exported filesystem.

Note also delaying the fi_had_conflict check we're able to return a
better error (hence give 4.1 clients a better idea why the delegation
failed; though note CONFLICT isn't an exact match here, as that's
supposed to indicate a current conflict, but all we know here is that
there was one recently).

Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Tested-by: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
[tuomasjjrasanen: backported to 3.10
   Conflicts fs/nfsd/nfs4state.c:
     Delegation type flags have been removed from upstream code. In 3.10-series,
     they still exists and therefore the commit caused few conflicts in function
     signatures.
]
Signed-off-by: Tuomas Räsänen <tuomasjjrasanen@opinsys.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>