'locales' package gets installed before '12-debian-locale-gen' is executed
and generates effectively empty /etc/locales.gen in debian, which makes
dpkg-reconfigure call to locales ignore the values set by
debconf-set-selections.
* Remove /etc/locale.gen generated by 'locales' installation to ensure
proper locales generation on debian images
* Remove 'locales-all' package installation from debian element since
it's not needed anymore to build the image and cosnumes additional
~120MB of space
* Remove unused 'package-installs' dependency from debian-minimal
element
Change-Id: Ic39ba2b5ceb5018efb75742547b2babf80827e56
Closes-Bug: #1452400
