Some of the tests in ssl_linear may fail sporadically, (or worse, falsely pass) if the system CA store still contains certificates left behind by previous resmoke runs on the same host machine. Tests that rely on the system CA store must therefore make sure that the system store is in a clean state (meaning it does not contain any of the keys & certificates used by the SSL tests). Avoid cherry-picking certs to delete by thumbprint, as it is not guaranteed to delete all the certs relevant to a particular test, especially when different versions of the test have imported various versions of that certificate.