fuse: Connection bit for enabling writeback

Off (0) by default. Will be used in the next patches and will be turned
on at the very end.

Change-Id: Icac47d3a3230fcc961dee94dd3c0c1830c79ac1a
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Git-commit:  d5cd66c58edf10a7ee786659994595fd43995aab
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git


Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>