scripts: Set the matchbox tag development and test run against
scripts: Set the matchbox tag development and test run against

* Stop using the latest tag, since this may be cached (i.e. rkt)

coreos/coreos-baremetal,dghubble/matchbox,enilfodne/matchbox,coreos/coreos-baremetal,enilfodne/matchbox,dghubble/matchbox