specify step when hijacking one-off builds
specify step when hijacking one-off builds

The new "check containers as steps change" causes there to be at least
two containers when doing a fly execute now. Previously it was always
one container and the step did not need to be specified.

Signed-off-by: Taylor Silva <33b075afcd0610c62dcb82fe76b4c1adc69221da@pivotal.io>
Co-authored-by: Sameer Vohra <331d3c3021287f48dfcf7707b8699b9bcecefef1@pivotal.io>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse