Exit scanConsole gracefully when only configuring frontends

What

As it stands currently, there is no "configure front-end utility", whose sole purpose is to send a configuration to a list of connected front-ends (based on the connectivity and controller configs). So, if one only wants to configure a front-end set, you have to run scanConsole and not provide the -s parameter specifying a scan.

Right now, this will basically get up to configuring the chips and then when it hits the stage of "building a scan", it will report a failure. This MR makes it simply exit scanConsole after the front end configuration stage if no scan configuration is provided, and will avoid printing out misleading errors.

Notes, 1

This MR currently exits immediately after the "front-end configuration" step, but before the checkCom() stage. Does it make more sense to do it after checkCom()?

Notes, 2

As a separate change, we should add a "configure front-ends only" utility/executable rather than relying on scanConsole, whose scope is much larger. Generally, a lot of the functionality now used in scanConsole should be made as part of some "utility" namespace so that one can do (e.g. the database setup), for example:

configure_frontend(fe, hw);