Fishtest server still has some race conditions

[tomtor]

@ppigazzini EDITTED: At various places runs are updated while they may be concurrently written to MongoDb. Eg update_spsa() might cause an exception when executing spsa["param_history"].append(summary).

This rare exception is from within the MongoDb replace_one code (dictionary size changed), and is catched and hopefully leaves the MongoDb driver in a consistent state.

Can be fixed by acquiring more run specific locks at various places but will not fix this unless it's a real reliability issue.