Switch to using busybox instead of sed.

[cheako]

I just got to the part when it installs the sed package. I think in most cases awk would be a better fit, but if we are going to be installing a tool for this task it's gotta be busybox. Example:
tunnelInterfaceIP="$(ip -br addr show dev "$tunnelInterface"|busybox awk -F'[ /]+' '{print$3}')"
Also busybox sed... so both needs are covered. In that case we should also target the busybox sh, meaning no more arrays I'd guess.