Separate FileAppender filename for org.perf4j.logback.AppenderTest

This is a test code issue. It does not impact tests currently on master HEAD, but I have hit issues when trying to add new tests, and believe that this is the cause. I get mysterious test failures I believe due to the separate logging subsystems writing to the same file(s).

The two AppenderTest s for log4j and new logback, and their config files log4j.xml and logback.xml point to the same output file ./target/statisticsLog.log. The same applies to the CSV tests and statisticsLog.log.

This issue proposes to shift the output filenames for the logback test setup ensuring that all test output is independent.