do not create _data dir without checking first
do not create _data dir without checking first

container_populate_volume() checks _data existance to determine if it
should populate old data. We only need to create new _data with 0777
mode if there is no existing one. That includes two cases:
1. before populating old data in container_populate_volume()
2. mount an empty volume for the fist time

For file volume case, we need to chmod it instead, to make sure any user
is able to read/write the file.

Signed-off-by: Peng Tao <39d8af57313740070ea49547576f55682fe5221a@gmail.com>

gnawux/hyperstart,MarioCarrilloA/hyperstart,laijs/hyperstart,hyperhq/hyperstart,gao-feng/hyperstart,MarioCarrilloA/hyperstart,gnawux/hyperstart,gao-feng/hyperstart,hyperhq/hyperstart,bergwolf/hyperstart,laijs/hyperstart,bergwolf/hyperstart,MarioCarrilloA/hyperstart,gnawux/hyperstart