This patch removes a couple of lines of redundant code. In Python,
the get method on a dictionary defaults the return value to None,
so the method never raises a key error.
https://docs.python.org/2/library/stdtypes.html#typesmapping
Change-Id: I180877f9be23d373cd63771bb3682d6587ec6fac
Adds a new pkg-map element which can be used to install
packages based on an in element 'pkg-map' JSON config
file format.
As part of this change we expose DIB's IMAGE_ELEMENT variable
so that we can have access to the element names which are being
installed in a clean manner.
This change is intended to decouple elements from DIB
and allow new elements to support multiple distributions
(with various package naming schemes) without having to
constantly maintain DIB's various bin/map-packages files.
Change-Id: Ic0a061995e2ae708c95a535cba6237bff58f7d93
