Avoid test pollution from randomized soldier test
Avoid test pollution from randomized soldier test

Ensure that the soldier exits before trying to examine the output
streams.

Signed-off-by: Johannes Petzold <688cf9f92d21a1bc04c0c50ee1ca49282872061e@pivotal.io>

cloudfoundry-incubator/buildpack_app_lifecycle,cloudfoundry-incubator/buildpack_app_lifecycle