Update homedir for non root user

[kjonick1]

This doesn't work with the container entrypoint script. That sets the HOME=/home/user. Ruby expects to find the aws credentials in ~/.aws. Otherwise, we get the following error:

Aws::Errors::MissingCredentialsError: unable to sign request without credentials set

[disaac]

LGTM

[disaac]

@kjonick1 On a side note we previously handled both the UID and GID when launching the container. This was changed to just use the UID which in most cases should be fine but on systems like Bamboo dumping artifacts from the container may be problematic depending on the permissions.

[yuhunglin]

@kjonick1 #63 is going to introduce some changes to where the gem is sourced from (and i'll need to make updates to the CI container), so we should probably merge this before that, or come back around and rebase this PR.