Allow multiple backups of hostapd configuration file

[jcapona]

The existing configuration is backed up when wifi-ap-sta starts and restored when it stops, but in case of a shutdown, the original configuration will be overwritten when wifi-ap-sta starts again.

The application should be able to store multiple backups of this configuration file so it's not lost/overwritten.

Maybe storing them using an sufix, e.g.: hostapd.conf.orig.1, hostapd.conf.orig.2 and so on, and use the latest when restoring the configuration.