C++ version of vold_create_subdirs needs extra permission

10-23 16:40:43.763  7991  7991 I auditd  : type=1400 audit(0.0:79): avc: denied { open } for comm="vold_prepare_su" path="/dev/pts/1" dev="devpts" ino=4 scontext=u:r:vold_prepare_subdirs:s0 tcontext=u:object_r:devpts:s0 tclass=chr_file permissive=0

Bug: 67901036
Test: Boot device, create user, create files, remove user, observe logs

Change-Id: I8d33dfd2a0b24611773001f20101db40aeb13632

public/vold_prepare_subdirs.te

@@ -8,7 +8,7 @@ typeattribute vold_prepare_subdirs coredomain;
 allow vold_prepare_subdirs system_file:file execute_no_trans;
 allow vold_prepare_subdirs shell_exec:file rx_file_perms;
 allow vold_prepare_subdirs toolbox_exec:file rx_file_perms;
-allow vold_prepare_subdirs devpts:chr_file { ioctl read write };
+allow vold_prepare_subdirs devpts:chr_file rw_file_perms;
 allow vold_prepare_subdirs vold:fd use;
 allow vold_prepare_subdirs vold:fifo_file { read write };
 allow vold_prepare_subdirs file_contexts_file:file r_file_perms;