Allow read access to /proc entries for other UIDs

Allow dumpstate (aka adb bugreport), servicemanager, and
surfaceflinger to access /proc entries associated with other UIDs.

Bug: 23310674
Change-Id: I385dcf0db3376ba979409cbe6fe1a468d36237ef
diff --git a/cmds/servicemanager/servicemanager.rc b/cmds/servicemanager/servicemanager.rc
index e73516d..b70fda7 100644
--- a/cmds/servicemanager/servicemanager.rc
+++ b/cmds/servicemanager/servicemanager.rc
@@ -1,7 +1,7 @@
 service servicemanager /system/bin/servicemanager
     class core
     user system
-    group system
+    group system readproc
     critical
     onrestart restart healthd
     onrestart restart zygote