Temporary workaround for coursier-based sbt launcher

Seems reload reloads sbt from the same classloader, which leaves the in
memory cache as is. When update is called, things are then picked from
the cache, and nothing gets logged, which makes the test fail.

modules/sbt-coursier/src/sbt-test/shared-1/logger/test

@@ -2,5 +2,6 @@ $ delete cache
 > update
 > checkDownloaded
 > reload
+> clean
 > update
 > checkFound