With --signcsr the private key never exists in the cert home, so every
renewal printed ".../domain.key: No such file or directory" from the
shell redirection. Skip the key read in that case; the install_ssl call
already ran with an empty key there and cPanel keeps the installed one.
https://github.com/acmesh-official/acme.sh/issues/6228
Eliminated php dependency with a private function for urlencode using sed. Php had failed on godaddy due to multiple php instances and naturally cron using the one without the necessary -r option. Compared to previous PR the sed code is now POSIX and should work on all environments.