allow run-as to carry unix_stream_sockets

Allow run-as to transmit unix_stream_sockets from the shell user to
Android apps. This is needed for Android Studio's profiling tool to
allow communcation between apps and debugging tools which run as the
shell user.

Bug: 35672396
Test: Functionality was tested by shukang
Test: policy compiles.
Change-Id: I2cc2e4cd5b9071cbc7d6f6b5b0b71595fecb455e