fix ClassTag cache leak
fix ClassTag cache leak

JDK issues about the problem:
* https://bugs.openjdk.java.net/browse/JDK-8136353

scala/scala,lrytz/scala,scala/scala,scala/scala,lrytz/scala,lrytz/scala,lrytz/scala,lrytz/scala,scala/scala,scala/scala,scala/scala,lrytz/scala