Small cleanup in AppLaunch.

closeApp is always force closing app. Just make it so.
Move the go home intent into its own method.

Test: adb shell "am instrument -w -e drop_cache true -e simpleperf_app true -e compiler_filters speed\|speed-profile\|quicken\|verify -e apps Maps^Maps -e launch_directory /data/local/tmp com.android.tests.applaunch/android.test.InstrumentationTestRunner"

Change-Id: I0d7d28a99a1ce9dfcefc4572ec3a0142482b1e48