Make relative paths in runtime mkdir be relative to container rootfs
Make relative paths in runtime mkdir be relative to container rootfs

Currently all paths were treated as absolute paths.

Signed-off-by: Justin Cormack <af64ee19f04db9509cb02b0e470e11e5402ef9b3@docker.com>

ndauten/linuxkit,thebsdbox/linuxkit,djs55/linuxkit,konstruktoid/linuxkit,justincormack/linuxkit,djs55/linuxkit,JohnnyLeone/linuxkit,djs55/linuxkit,thebsdbox/linuxkit,YuPengZTE/linuxkit,thebsdbox/linuxkit,yankcrime/linuxkit,YuPengZTE/linuxkit,linuxkit/linuxkit,justincormack/linuxkit,zx2c4/linuxkit,rn/linuxkit,thebsdbox/linuxkit,furious-luke/linuxkit,rn/linuxkit,ndauten/linuxkit,furious-luke/linuxkit,linuxkit/linuxkit,ndauten/linuxkit,rn/linuxkit,JohnnyLeone/linuxkit,djs55/linuxkit,thebsdbox/linuxkit,thebsdbox/linuxkit,YuPengZTE/linuxkit,furious-luke/linuxkit,furious-luke/linuxkit,linuxkit/linuxkit,rn/linuxkit,konstruktoid/linuxkit,deitch/linuxkit,yankcrime/linuxkit,konstruktoid/linuxkit,konstruktoid/linuxkit,YuPengZTE/linuxkit,ndauten/linuxkit,linuxkit/linuxkit,justincormack/linuxkit,justincormack/linuxkit,yankcrime/linuxkit,YuPengZTE/linuxkit,zx2c4/linuxkit,zx2c4/linuxkit,zx2c4/linuxkit,yankcrime/linuxkit,ndauten/linuxkit,YuPengZTE/linuxkit,justincormack/linuxkit,deitch/linuxkit,deitch/linuxkit,justincormack/linuxkit,deitch/linuxkit,zx2c4/linuxkit,yankcrime/linuxkit,deitch/linuxkit,JohnnyLeone/linuxkit,furious-luke/linuxkit,konstruktoid/linuxkit,JohnnyLeone/linuxkit,ndauten/linuxkit,konstruktoid/linuxkit,JohnnyLeone/linuxkit,yankcrime/linuxkit,linuxkit/linuxkit,djs55/linuxkit,rn/linuxkit