[update-config] order of sections is modified

[okraits]

This is an issue similar to #60 and #64. openwisp-update-config.lua modifies the order of sections in uci files. This can lead to unwanted behaviour especially in the firewall configuration where the order of the sections is critical.

I noticed it when I tried to modify a section which was not created by openwisp-config. After the first modification the order is still the same, but it changes with the second modification.

[nemesifier]

@okraits argh, I'm sorry this is happening. What approach do you want to use in fixing this?