fix in mount.glusterfs for proper direct io mode option.
fix in mount.glusterfs for proper direct io mode option.

fixes the bug which causes GlusterFS not to have valid 'direct-io'
option through mount command or /etc/fstab entries.

Signed-off-by: Anand V. Avati <6a1810c170bd423868ce2e225ecea39d80cade0f@amp.gluster.com>

Kaushikbv/Gluster,Kaushikbv/Gluster,Kaushikbv/Gluster