Revert "Revert "Revert "Revert some flaky unloading"""

Ensure that all threads are in the JNI code before destroying the
runtime.

Bug: 28406866

This reverts commit b2716bbf321293ddbd0b96f0ea999794b0e9b09b.

Change-Id: I7f6189a9d0d8a1bf7af5535026804bc2183466c9
3 files changed