Ubiquiti removed keytool (and java) from recent releases of Unifi OS. This moves from keytool to openssl's native pkcs12.
Tested on Unifi Dream Machine which runs Unifi OS and a built-in Unifi controller.
Also added backup of existing files prior to change in case anything goes wrong, and update system configuration with compatible ciphers.
* first version dns_rcode0.sh
* fixed URLs for ACME calls
* fixed challenge remove
* read & write Token/URL at rm too
* make info messages debug
* typos fixed
* update rrset only if existing challenge is found
* polish error messages and make "detect root zone" scaleable
* fixed formating issues
* code cleanup, remove some unneeded functions
* removed empty lines
* save rcode0 url only if not default