Add ability to see that the status of a previous container was

A specific use case for the boot looper checker is that machine_registration follows this pattern: b2c.container="... check" b2c.container="... boot_success", that is, first check if the DUT's hardware has changed, if not, tell the looper to increase its boot count, if so, reset the count.

For this logic to work, the second container needs to return code of the first.