Upgrade WiFi Access Point Firmware

Upgrade via the UI should work, if not, try:

1. SCP the *.bin file to /tmp/fwupdate.bin
2. SSH to AP, and issue: syswrapper.sh upgrade2 & (backgrounding is important!)

If it's still being difficult, then try the following:

1. Cache the relevant firmware using the Unifi UI
2. Stop the Unifi controller
3. SSH to AP, and issue: defaultsyswrapper.sh restore-default
4. Username / password will be ubnt/ubnt after this
5. SCP the *.bin file to /tmp/fwupdate.bin
6. SSH to AP, and issue: syswrapper.sh upgrade2 & (backgrounding is important!)
7. Wait for AP to restart
8. Start Unifi controller
9. AP should be re-adopted