Currently the ARA database is not collected after each
test, nor is the reporting done as it should be. This
patch does the following to resolve that:
1. Informs the log collection to collect to and from
the right source folder.
2. Verifies that the logs directory exists to ensure
that a missing directory does not cause the job to
fail.
3. Makes the log collection quiet, so that only errors
are reported when pulling them back to the zuul
executor.
4. Removes a layer of indirection by making zuul use
the scripts library directly instead of working
through yet another wrapper script.
5. Sets the exit code properly so that the ARA report
is run on test execution failure.
Change-Id: Ie8da165a33180d03c840a69dae0aa5f424a69e50