Moved some thread priority changes.

The previous place I had moved these changes resulted in runtime threads
being created at the wrong priority.  This patch moves the calls to the
correct location.

Test: atest CtsJvmtiRunTest924HostTestCases
Bug: 146614089
Change-Id: Iad2e17cd137eab81c595cb6816608a36b009da8b
Merged-In: Iad2e17cd137eab81c595cb6816608a36b009da8b