Allow 'vdc' to be invoked with logwrapper.

Currently vdc emits logs to stderr, which makes sense for command
line invocations, but when exec'ed they're silently dropped unless
the caller uses logwrapper.

avc: denied { read write } for path="/dev/pts/2" dev="devpts" ino=5 scontext=u:r:vdc:s0 tcontext=u:object_r:devpts:s0 tclass=chr_file permissive=0

Bug: 25796509
Change-Id: Ib92e0a7f580b1934a9853a83684f95b24bdc355c

vdc.te

@@ -21,3 +21,6 @@ allow vdc shell_data_file:file { write getattr };
 
 # Why?
 allow vdc dumpstate:unix_dgram_socket { read write };
+
+# vdc can be invoked with logwrapper, so let it write to pty
+allow vdc devpts:chr_file rw_file_perms;