Refactor fuel-web's run_tests.sh

Purpose: get rid of unclear logic. It includes the following
improvements:

* run tests from one place
* increase code readability
* function decomposition

Change-Id: Id4578327f7f50c2862b4fc7776ed8b60552dde6b
Closes-Bug: #1282116
Merge "Refactor fuel-web's run_tests.sh"