Set appropriate log level in pmd-maven-plugin

[delanym]

The org.apache.maven.plugins.pmd.PmdViolationCheckMojo goal logs violations at "info" level.
See example at #4001

I filter Maven log output based on the log level, so I miss these after setting printFailingErrors to true.

If the failOnViolation is true, I expect violations logged at error level.
If the failOnViolation is false, I expect violations logged at warning level.

[jsotuyod]

This repository is about PMD itself. Maven PMD Plugin lives at apache.org -> https://issues.apache.org/jira/projects/MPMD/summary

As for pmd itself, the failOnViolation flag (or equivalent, depending on whether this is a cli, ant or programmatic invocation) should not affect where errors are reported. Failure is determined by the output (build status, status code, etc) and not the channel.