Retain user specified order of post build scripts

Avoid imposing hardcoded order of the scripts within the module and
instead favour the order of the input data. Combined with use of ordered
dicts for yaml, this ensures that users may control the order of the
various steps to use with the post build scripts from yaml.

Change-Id: Icf540a53cb6f1b13f80f09d9103610aee10d3861
Merge "Retain user specified order of post build scripts"