FIX CN parsing to work with OpenSSL 1.1

diafygi/acme-tiny@9537453

CN used to be without whitespaces around the `=` but OpenSSL 1.1 introduced
whitespaces:
1.0.1: subject=/CN=example.com
1.1.0: subject=CN = example.com

This commit makes them optional.

webmin/acme_tiny.py

@@ -78,7 +78,7 @@ def _send_signed_request(url, payload):
     if proc.returncode != 0:
         raise IOError("Error loading {0}: {1}".format(csr, err))
     domains = set([])
-    common_name = re.search(r"Subject:.*? CN=([^\s,;/]+)", out.decode('utf8'))
+    common_name = re.search(r"Subject:.*? CN\s?=\s?([^\s,;/]+)", out.decode('utf8'))
     if common_name is not None:
         domains.add(common_name.group(1))
     alt_names = re.search(r"Subject:.*subjectAltName=([^\s,;/]+)", out.decode('utf8'))