Do not always use Level.Debug while creating a backgroundLog
Do not always use Level.Debug while creating a backgroundLog

The creation of a backgroundLog was always using Debug as the
logging level for console and backing. This commit sets the
levels to those used by the caller. Fixes #3655

mdedetrich/sbt,sbt/sbt,mdedetrich/sbt,sbt/sbt,mdedetrich/sbt,sbt/sbt,sbt/sbt,xuwei-k/xsbt,xuwei-k/xsbt,sbt/sbt,sbt/sbt,sbt/sbt,mdedetrich/sbt,mdedetrich/sbt,xuwei-k/xsbt,mdedetrich/sbt,mdedetrich/sbt,xuwei-k/xsbt,xuwei-k/xsbt