- It was running too late.
 - Wasn't actually using `shellOnFail` config

The service and mount points are more of an implementation detail of the
GadgetFS handling library and not an implementation detail of the init
library.

In turn, this means that we are decoupling this from the init, follow-up
on the next commit...

(Though it may require fiddling with udev perms)

FunctionFS on GadgetFS requires this to happen in order:

 - (1) preparing the gadget
 - (2) preparing the function
 - (3) mounting the functionfs
 - (4) starting the daemon
 - (5) enabling the device

Doing any of these steps in the wrong order *will* fail. You cannot
mount functionfs if the function name hasn't been allocated yet. You
cannot start the daemon without functionfs being mounted. You cannot
enable the device without the daemon running on the USB endpoints.

This is why the GadgetFS stuff here *has* to know about mounting the
filesystem and starting the daemon.

In fact, the generic library to be written to handle USB gadget mode
**will** have to have that knowledge!

The added TODOs are to be done when extracting as a standalone library.

Also warn if it could not be enabled.

Also warn if it could not be enabled.

Enable ADB with GadgetFS devices