StrictMode detectAll() based on target API level.

Some apps are asking StrictMode to detectAll(), but we should only
trigger the violation types that they would expect based on their
target SDK level.  (This prevents us from starting to yell about
violations in new API levels that a developer never would have known
about.)

Test: builds, boots, older apps aren't triggered
Bug: 34735225
Change-Id: Idff1bfdf57c635b828236e34a24d55350b9fa556