mount.glusterfs: use option --direct-io-mode instead of --disable-direct-io-mode
mount.glusterfs: use option --direct-io-mode instead of --disable-direct-io-mode

Signed-off-by: Raghavendra G <raghavendra@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 2173 (enabling/disabling direct-io mode is not possible when glusterfs is mounted using mount command)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=2173

Kaushikbv/Gluster,Kaushikbv/Gluster,Kaushikbv/Gluster