make su an mlstrustedsubject

Otherwise the following denial occurs when I3972f846ff5e7363799ba521f1258d662b18d64e
is present and "adb root" is run.

  <6>[   64.507223] type=1400 audit(1411432079.100:471): avc: denied { connectto } for pid=717 comm="JDWP" path=006A6477702D636F6E74726F6C scontext=u:r:untrusted_app:s0:c512,c768 tcontext=u:r:su:s0 tclass=unix_stream_socket permissive=1
  <6>[   64.507617] type=1400 audit(1411432079.100:472): avc: denied { connectto } for pid=1659 comm="JDWP" path=006A6477702D636F6E74726F6C scontext=u:r:platform_app:s0:c512,c768 tcontext=u:r:su:s0 tclass=unix_stream_socket permissive=1

Change-Id: I1772912b2ca1446b822303ad6ea3154427f8331f