Fix the servername used in log file name

The servername can be [schema://]hostname.domain[:port]. In the case of servername including schema and port, it is not appropriate to use as log file name. It will generate something like this: "ErrorLog /var/log/httpd/https://domain_error.log", which cause httpd failed to refresh/start.
Merge pull request #547 from xcompass/fix-servername-in-logfile

Fix the servername used in log file name