Fix csyslogd-config XML syslog location definition

The documentation regarding the syslog_output configuration options states that a _location_ parameter is supported (see http://ossec-docs.readthedocs.org/en/latest/manual/output/syslog-output.html#element-location).

The csyslogd config parser was actually expecting an *event_location* parameter. I thought it best to match the documentation. This simple fix does the job for me.