LU-812 llite: 3.0+ kernel fsync should call write

LU-812 llite: 3.0+ kernel fsync should call write

Since 3.0, kernel pushes i_mutex and fsync to fs fsync
callback. So Lustre should check and do the same. Otherwise
there might be data corruption and sanity 63b will fail.

Signed-off-by: Peng Tao <tao.peng@emc.com>
Change-Id: I2f2f6792276eaf6783bffb813f3c3e5405be0450
Reviewed-on: http://review.whamcloud.com/4091
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>