Currently when running system tests, ctest has a default timeout of 1500 seconds which is way too long. So for example, system_tests_edge_router if it should hang for some reason, gets terminated by ctest only after 1500 seconds (25 mins). This is way too long.
We need to set a smaller more reasonable timeout per test for ctest.
system_tests_edge_router is the longest executing test in the test suite. Looking at how long it takes to execute on a slow Travis system, we have reached the conclusion that 300 seconds would be a good timeout value for ctest.