Remove dead code related to shutdown hooks.

Both java.lang.Shutdown and java.lang.ApplicationShutdownHooks are
building blocks of the OpenJdk Runtime#addShutdownHook implementation.

It is not used in the Android port: there is a simpler implementation added in java.lang.Runtime.

This change makes further OpenJdk 8 pulls simpler.

Bug: 28666126
Change-Id: I3a15f3e8d00432360b46e1b8f9ef22797f1b743b
7 files changed