acme: Backport two bug fixes from master

This backports the following bug-fix commits from the master branch:

c6b4d7f367 ("acme: Include empty 'dns' config option by default")
983cc995a3 ("acme: Correctly handle domain state dir for ECC certificates")

Fixes #11675.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>

net/acme/files/acme.config

@@ -10,4 +10,5 @@ config cert 'example'
        option update_uhttpd 1
        option update_nginx 1
        option webroot ""
+       option dns ""
        list domains example.org