Boolean options that default as `None` but are set to `False` by the user were ignored on update. This change checks to distinguish None & False so that options like multi_az can be turned off during an update.
* Modifying how optional parameters are handled in rds.py. Fixes#20370
Allowing options to be set to false/no. Previously ignored unless set to true/yes.
Added a conditional for invalid parameters since the default is false instead of null for some options (e.g. force_failover, apply_immediately, upgrade).
* Making requested revision.