fixes VaultSecrets test - it was failing due to a
regex mismatch (`^job` stopped matching when
copywrite headers got prepended to the jobspec).
but RegisterFromJobspec (which had the bug)
was only used in the one spot, so instead this
refactors the whole test to the v3 format
with testing.T and some additional fun stuff
that we can take advantage of with it.
some improvements:
* use a namespace
* use and extend existing test helpers
* add more test helpers
If any E2E test hangs, it'll eventually timeout and panic, causing the
all the remaining tests to fail. External commands should use a short
context whenever possible so we can fail the test quickly and move on
to the next test.
The E2E suite exercises the API, but not the CLI. This changeset adds a helper
function to send commands via a locally-built Nomad binary (which we'll need
to add to the E2E setup), and some helpers to parse the resulting structured
outputs in a way that tests can consume.
