[COOK-3825] homebrew_package needs $HOME set

https://tickets.opscode.com/browse/COOK-3825

When running chef solo/client as root, brew package doesn't get the $HOME environment variable - which means package installs fail when trying to log.

See this gist for error output: https://gist.github.com/walkah/d56d4b52ef893a36aa61

This PR explicitly sets $HOME for homebrew_owner during shell_out.