releasetools: Use java_path in sign_target_files_apks.py.
Prior to this CL, it was calling the hard-coded "java" although it was
accepting a "--java_path" option.
Also switch OPTIONS.java_args from string to list. Otherwise it won't
work when providing multiple args.
Bug:
32737832
Test: Specify "--java_path=" and "--java_args" when invoking
sign_target_files_apks.py with "-v". Check the commands being
called.
Change-Id: Id7ef98e778646d532027434de7fba9b7a104dbd0
(cherry picked from commit
e95540e06000f3b0b33bf12374135111ecf45bd5)