Dropping join indexes on a write server [CR 385317]

You can no longer drop a join index on a write server if the FORCE_DROP option is set ON. To force drop such a join index, you must first start the server in single-node mode. If you drop an object when FORCE_DROP = ON, the FORCE_DROP setting on query servers is unaffected. and you need only restart the write server after the drop completes.