kata_agent: Create and start container implementations
kata_agent: Create and start container implementations

Create adds the rootfs and all container mounts.
It also sets the OCI rootfs path properly.

Start simply sends the StartContainer gRPC command.

Signed-off-by: Samuel Ortiz <0ba86cb3f08bbb861958e54bd3438887adb4263c@linux.intel.com>

containers/virtcontainers,containers/virtcontainers