apps:run test with lengthy output -- don't log actual output on failure

[Cryptophobia]

From @vdice on May 26, 2017 22:17

When/if this apps:run test fails, the Expect statement proceeds to log the entire command's output, corrupting the user's terminal and crowding out logs with byte code.

We should re-jigger the test, perhaps checking first if the byte array does not match expected (outside of Expect) and then, if not, logging some standard error/failure message accordingly.

Copied from original issue: deis/workflow-e2e#360

[Cryptophobia]

From @vdice on May 31, 2017 0:3

Alas, since the output is stored in sess.Out.ContentsI(), Ginkgo will log this anytime the test fails (no matter how test is failed). Wondering if there's another way to eliminate logging of output? Or, another way to test this case? ping @mboersma