Reduce log noise coming from File sink

[kennknowles]

After switching to Beam 2.2 I noticed that File sink related classes generate lots of lines likes this:

2018-01-16 01:37:37,080 INFO org.apache.beam.sdk.io.FileBasedSink - No output files to write.
2018-01-16
01:37:37,104 INFO org.apache.beam.sdk.io.WriteFiles - Will finalize 0 files

 

I did some counts and it looks like this lines account for 82% of all lines in the log yet not giving much information.

I am happy to raise a PR to make "No output files to write." and "Will finalize {} files" logged at DEBUG level.

Imported from Jira BEAM-3488. Original Jira may contain additional context.
Reported by: pawelbartoszek.