Remove transaction ids in IActivityManager.aidl.

Bug: 30977067
Test: cts/hostsidetests/services/activityandwindowmanager/util/run-test \
          android.server.cts
      adb shell am instrument -e class \
          com.android.server.am.ActivityManagerTest,com.android.server.am.TaskStackChangedListenerTest \
          -w com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I44c5f756db882e0400727e44264219c873e6bd02