Harden security for requests

We also need to harden security for options parameters stored in `MiqRequest` and `MiqRequestTask`.

They are encoded a little differently from Configurations (stored `vmdb.yml`) - so need to make sure those parameters are covered.

Tried to keep this change to as few files as possible. May need to backport. Couldn't bring myself to rewrite the `ConfigurationEncoder` serialization routines that may not be used in `MiqRequest`, but are very close.

https://bugzilla.redhat.com/show_bug.cgi?id=1151241

/cc @jdeubel @gmcculloug