nfsd: remove unneeded EEXIST error check in nfsd_do_file_acquire

Given that we do the search and insertion while holding the i_lock, I
don't think it's possible for us to get EEXIST here. Remove this case.

Fixes: c6593366c0 ("nfsd: don't kill nfsd_files because of lease break error")
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Youzhong Yang <youzhong@gmail.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/filecache.c

@@ -1037,8 +1037,6 @@ retry:
 	if (likely(ret == 0))
 		goto open_file;
 
-	if (ret == -EEXIST)
-		goto retry;
 	trace_nfsd_file_insert_err(rqstp, inode, may_flags, ret);
 	status = nfserr_jukebox;
 	goto construction_err;