Small but important tweaks to fix the operation of the nut initscripts
and hotplug scripts.  All hail shellcheck and proofreading and
dogfooding.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>

The mechanism for making sure hotplug doesn't execute during forced shutdown
was interfering with initial start of hotplug script due to checking for path
that doesn't exist at initial start.  This fixes that and closes #6966.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>

usbhid-ups has the necessary information in the source, so
let's support USB hotplugging out of the box.  Takes advantage of
the procd support now in nut-server initscript.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>