add an export option

Add an option to export the list of packages that got installed
to the mirror so that we can use the list to compare
the difference between the requirements (packages to be installed)
and the mirror (what actually got installed)

Change-Id: Ifda23d78ea4f324a145fc0279f4c80dc25570f73
Related-Bug: #1172417
Merge "add an export option"