releasetools: Use java_path in sign_target_files_apks.py. am: cd4f7c96c0 am: 6414a94c50 am: 4722fc1734 am: e6a27e7e69 am: 02dd0ab453
am: 5427f6aa75

Change-Id: I2c435132e977056dd1b996734f3ddd003144b186