Automatic merge from submit-queue
rkt: Use volumes from RunContainerOptions
This replaces the previous creation of mounts from the `volumeGetter`
with mounts provided via RunContainerOptions.
This is motivated by the fact that the latter has a more complete set of
mounts (e.g. the `/etc/hosts` one created in kubelet.go in the case an IP is available).
This does not induce further e2e failures as far as I can tell.
cc @yifan-gu