Merge pull request #2302 in SNORT/snort3 from ~RUCOMBS/snort3:disable to master

Merge pull request #2302 in SNORT/snort3 from ~RUCOMBS/snort3:disable to master

Squashed commit of the following:

commit 7727770ef9e075cb537853274ee559995b2213ad
Author: russ <rucombs@cisco.com>
Date:   Mon Jun 29 18:09:55 2020 -0400

    inspectors: add a virtual disable method for controls

    In some cases, a complex configuration may include unnecessary control
    inspectors.  The disable method allows them to tell the framework to not
    call them at runtime.  This does not apply to non-control inspectors.
    The best approach is not configure unnecessary inspection in the first
    place.