Spread tests through different test threads for better time usage. Fix pep8.

Change-Id: Ibc966e025df9fd2feef2f1df50c36ef6270dab32
Add destroy environment after test run into system_test shell script

Change-Id: I8cef8edabb5ad27b735c2b747baa4039218a8f75
Merge "Spread tests through different test threads for better time usage. Fix pep8."