corrected parser error/configuration for "vm endpoint acl-rule create"

Hey Guys,

This pull request resolves #1500 whereby `--description` on `vm endpoint acl-rule create` would crash the command line tools. Really simple omission of `<description>` resulted in your parser passing in a `bool` instead of a `string` into the description validation logic.

Regards,
Geoff

(contribution as per CLA; documents are signed)