Override branch name `master` with the correct release branch when installing

ECOM-7207

We already do this in the common role but not in bootstrap or abbey roles.

Use my-passwords.yml in sandbox.sh

Update common to pull down the non-ppa python on 16.04

This prevented the -b option to install_stack.sh from working properly.

Now the install happens in the current directory, with logs in a 'logs'
subdirectory.

Other improvements: curl now fails if the Vagrantfile can't be
downloaded, because the RELEASE value is invalid.  Curl also doesn't
print as large a progress bar.  The script fails early if there's no
RELEASE specified.

(cherry picked from commit 66a25250)

Now the install happens in the current directory, with logs in a 'logs'
subdirectory.

Other improvements: curl now fails if the Vagrantfile can't be
downloaded, because the RELEASE value is invalid.  Curl also doesn't
print as large a progress bar.  The script fails early if there's no
RELEASE specified.

(cherry picked from commit a8bd50f9)