Remove thread shutdown logic.

This logic wasn't right, and the kernel will clean
it up anyway. Since loading and unloading this library
isn't supported, I'm removing this race-prone section
of code until someone has a reason to and decides to
support this usecase.

Bug: 77934844
Test: (walleye) device boots/shutdowns w/o fatal errors
Test: (walleye) system/tools/hidl/test/run_all_device_tests.sh
Change-Id: I638f1741bf9d47e4113e65ecae8c9b278cee0cfa
1 file changed