Add goose to the PATH and log to stdout

[zrhoffman]

What does this PR (Pull Request) do?

• • This PR fixes an issue sometimes encountered when running the Postinstall script under Python 2:

DEBUG:root:psql exec failed; stderr: <open file '<fdopen>', mode 'rU' at 0x7fb7a8e3af60>
        stdout: <open file '<fdopen>', mode 'rU' at 0x7fb7a8e3aed0>
ERROR:root:Failed to set up database: failed to execute database query

• Adds /opt/traffic_ops/app/bin to the PATH by sourcing /etc/profile.d/traffic_ops.sh.

• Makes the Python implementation of Postinstall log to stdout, not stderr, because that is what the Perl version does

Which Traffic Control components are affected by this PR?

• Traffic Ops Postinstall script

What is the best way to verify this PR?

• Run the Postinstall unit tests
• Ensure CDN in a Box runs successfully

If this is a bug fix, what versions of Traffic Control are affected?

• master (150cbdc)

The following criteria are ALL met by this PR

• This PR includes tests
• Bugfix, no documentation necessary
• An update to CHANGELOG.md is not necessary
• This PR includes any and all required license headers
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

[ocket8888]

Tests still pass, showing that logging to stdout - for an interactive program, for some reason - is working.