Add possibility invoke run_tests with coverage
Add possibility invoke run_tests with coverage

Add possibility invoke run_tests with coverage:
if we run ./run_tests.sh -c, testropt
consists --with-coverage --cover fuel_plugin
Closes-Bug: #1478981

Change-Id: Id09b0a7bcb6b2b1189c0a1d4d47f42b82429a957

eayunstack/fuel-ostf,stackforge/fuel-ostf,stackforge/fuel-ostf,eayunstack/fuel-ostf