Refactoring build-app and unittest-app

Created app-common
Replaced with tlog function with TLOG
Added elapsed function, replaced print_end_timestamp
Replaced get_image_id with app_glance_id
Replaced run_timed_command with PRUN
Removed use of EXIT_STATUS
Replaced argument -z tests with $# test
Prepended docker unittest with PRUN
Removed commented code and other cleanup

Change-Id: Ibd9374524541c49d20625d58db1c005351d79c8f
Merge "Refactoring build-app and unittest-app"