fix #90 Classic Test Runner: unable to reload test suite

When using AT <1.6.1, timestamped requests for `MainTestSuite` were sent
but the server ignored them. This commit allows timestamped requests
which fixes the issue with reloading test suites.
Classic Test Runner: use `runIsolated` by default

The link "Debug this campaign" on attester status page
now leads to the page which runs each test in isolation,
which helps avoiding certain errors if the test modifies
global execution environment.