From: viro@parcelfarce.linux.theplanet.co.uk

bernhard_heibler@gmx.de has discovered that NFS is very slow when writing to
a file which has execute permissions.  See

	http://bugme.osdl.org/show_bug.cgi?id=1936

This patch fixes remove_suid() to not try to modify the inode mode on every
write to such a file.