convert string type port parameter into int type

In our cluster, we use syslog to collect reframe tests data. We have found SysLogHandler require int type port instead of str type in codes now. It works fine in our cluster after change.

Author: difey

reframe/core/logging.py

@@ -222,7 +222,7 @@ def _create_syslog_handler(site_config, config_prefix):
     except ValueError:
         pass
     else:
-        address = (host, port)
+        address = (host, int(port))
 
     facility = site_config.get(f'{config_prefix}/facility')
     try: