sepolicy: add policy file for USTA test app

USTA is a system app which interacts with fastRPC to communicate
to SLPI. There are changes in fastRPC to access require DAC and MAC
permissions, required only by USTA test app. Adding separate domain
for USTA app.

Change-Id: I89c1beff1c10d341e678f7ae654dc16d2c184a83