(TouchMode Permission 2.6/n) Revert Instrumentation#setInTouchMode

Allow Instrumentation#setInTouchMode to always switch touch mode when
running in instrumented environment.

Bug: 198487159
Fixes: 218118731
Test: atest FrameworksCoreTests
Test: atest CtsWindowManagerDeviceTestCases
Test: atest android.app.cts.ListActivityTest
Test: atest AlertDialog_BuilderCursorTest
Change-Id: I22e4bf0245dcf75a354f2cdc19d7f6107d0abaee