Another round of Kobo Fixes (#3939)

* Trim unneeded stuff from startup script

I was somehow convinced I'd already done that...
While we're there, explain why we need to siphon those specific vars

* Fix a stray eth0

-> $INTERFACE

* Be very very sure we have INTERFACE set in our env

re #3936

* Make getFirmwareVersion less fragile on Kobo

Not that we actually use it right now, but, still. :D

* Use the same syntax as the PRODUCT check

* Actually implement getProductId

Instead of a stray c/p ^^

* Properly identify the Rev2/Mark7 variants of existing devices

Namely, the H2O² and Aura SE
Not that the H2O²r2 support is still broken, this just allows us to
implement it cleanyl without breaking handling of the original H2O²

re #3925

* Tweak sleeps a bit around Kobo WiFi modules...

See if that jog things up (re #3936)

* Try harder not to suspend with WiFi on on Kobos

Because otherwise, things go boom. (re #3936)

spec/unit/device_spec.lua

@@ -71,7 +71,7 @@ describe("device module", function()
                 if key == "PRODUCT" then
                     return "trilogy"
                 else
-                    return saved_getenv(key)
+                    return osgetenv(key)
                 end
             end)
 
@@ -118,7 +118,7 @@ describe("device module", function()
                 if key == "PRODUCT" then
                     return "trilogy"
                 else
-                    return saved_getenv(key)
+                    return osgetenv(key)
                 end
             end)
             local kobo_dev = require("device/kobo/device")