REGTEST: make the tls_health_checks test much faster

REGTEST: make the tls_health_checks test much faster

This test relies on a server timeout and was using the default 2s check
interval with a full 1s server timeout, thus adding a whole second to the
test series by itself. Let's shrink the server timeout to 20ms which is
way enough to properly trigger a timeout, and set the check interval to
the double of this, or 40ms.