mvn clean does not clean up target directories and build logs from integration tests

After adding an integration test for MWAR-131, I noticed that 'mvn clean' didn't clean up after it properly.

$ mvn install; mvn clean
$ svn status
? src/it/MWAR-131/build.log
? src/it/MWAR-131/mwar131-webapp/target
? src/it/MWAR-131/mwar131-test/target
? src/it/MWAR-131/mwar131-webapp2/target

However:

$ find . -name target
./src/it/MWAR-129/target
./src/it/MWAR-131/mwar131-test/target
./src/it/MWAR-131/mwar131-webapp/target
./src/it/MWAR-131/mwar131-webapp2/target
./src/it/MWAR-139/target
./src/it/MWAR-143/war-common/target
./src/it/MWAR-143/war-filter-overlay/target
./src/it/MWAR-62/target
./src/it/MWAR-96/target
./src/it/scoped-dependency-same-artifact/target
./src/it/simple-war-no-webxml/target
./src/it/simple-war-project/target

$ find . -name build.log
./src/it/MWAR-129/build.log
./src/it/MWAR-131/build.log
./src/it/MWAR-139/build.log
./src/it/MWAR-143/build.log
./src/it/MWAR-62/build.log
./src/it/MWAR-96/build.log
./src/it/scoped-dependency-same-artifact/build.log
./src/it/simple-war-no-webxml/build.log
./src/it/simple-war-project/build.log

Instead of the clean plugin being configured to delete these files, the svn:ignore property is set.