In some places of which network environment was limited, ciro can't
pull images from k8s.gcr.io. This patch add a variable
`CRIO_PAUSE_IMAGE` in order to the developer who located in these
places can set the ciro to pull pause container images from
repository that they can access.
The `CRIO_PAUSE_COMMAND` used to configure crio's `pause_command`
(the pause container's bootstrap command), in order to the developer
can use the special pause image the they customized.
Change-Id: Ib0d4c42870d40ef583546758513a36b906c7663b
f935202d39