Allow run-as to read/write unix_stream_sockets created by adbd.

This is to Allow commands like `adb shell run-as ...`.

Bug: http://b/62358246
Test: run commands manually.
Change-Id: I7bb6c79a6e27ff1224a80c6ddeffb7f27f492bb2
(cherry picked from commit 1847a38b)

public/runas.te

@@ -2,6 +2,7 @@ type runas, domain, mlstrustedsubject;
 type runas_exec, exec_type, file_type;
 
 allow runas adbd:process sigchld;
+allow runas adbd:unix_stream_socket { read write };
 allow runas shell:fd use;
 allow runas shell:fifo_file { read write };
 allow runas shell:unix_stream_socket { read write };