Move the test server port range below the ephemeral port range.

The ports assigned to the tests started at 34343, which is inside the ephemeral port range on Linux (32768-60999). A test that binds a port in that range can fail when the port is already in use as the source port of an outgoing connection, since SO_REUSEADDR only allows the bind when the conflicting socket is in TIME_WAIT.

Assign the test ports from below the ephemeral port range instead. No module requests more than eight ports, so reducing the maximum per test from 768 to 64 leaves ample headroom and allows the range for all 32 tests to fit in 30720-32767, i.e. ending exactly where the ephemeral port range begins.