Update docker entrypoint to fail on error

[found-it]

What this PR does / why we need it:

Proposed enhancement

Use set inside the entrypoint so it hard fails whenever there are errors.

Which issue this PR fixes (optional, in fixes #<issue number>)(, fixes #<issue_number, ...) format, will close the issue when PR is merged: fixes #:

Special notes:

To test

mkdir -p /tmp/certs
openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:2048 -keyout /tmp/certs/anchore.key -out /tmp/certs/anchore.crt
# fill out all info with junk, fields don't matter for test

make build
docker run -v /tmp/certs/:/home/anchore/certs/ anchore-engine:dev cat /home/anchore/certs_override/python/cacert.pem

[Vijay-P]

@found-it pretty sure this partially conflicts with what's currently in master. I think we already have the certifi fix in. Can you rebase please?

[zhill]

Can this be squash-merged to only have 1 commit instead of 7 since the changeset is fairly small?