*8854* Added tests for getRemoteAddr trust_x_forwarded_for config setting

Added unit tests for http://pkp.sfu.ca/bugzilla/show_bug.cgi?id=8854
It shouldn't be necessary to code test-specific stuff in setUp. If you just back up the config data here regardless of the test, then restore it in tearDown, you'll add negligible overhead and it'll be more maintainable.