Restart snowflake-server on snowflake-01 with num-turbotunnel=4

We are hitting a performance ceiling at about 475 MiB/s TX. The CPUs are not fully saturated: they are averaging about 87%. Currently we have num-turbotunnel=2. I want to try increasing this to num-turbotunnel=4 to see if the KCP state machines are again a bottleneck.

Cf. #40200 (closed)/!119 (merged) which effectively changed from num-turbotunnel=1 to num-turbotunnel=2. /cc @linus