Fix race condition in snowflake broker
There is a race condition with the snowflake heap that has been causing the broker to crash several times a day. This race condition has existed in the broker for several years, but some recent updates as well as the host migration managed to shake it loose.
This race condition is causing the snowflake broker to crash repeatedly and often since the migration. We noticed because CollecTor stopped collecting metrics since the restart on 14 November 2019.