tzdatacheck: don't hard code SELinux domain name

An automatic domain transition is already defined by SELinux
policy. Avoid having redundant information on the exec line.

This commit depends on commit 17fff893c04971b519d25d52b07f51111353cba5
which made the SELinux process label optional.

(cherrypicked from commit 221fca7ddd2ba1778ec89013c96434a9d36b529e)

Change-Id: I89464f2bd218c7d6e8db08aa6bed2b62ec6dad2a
diff --git a/rootdir/init.rc b/rootdir/init.rc
index d0768b2..b5ee98b 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -328,7 +328,7 @@
     restorecon_recursive /data
 
     # Check any timezone data in /data is newer than the copy in /system, delete if not.
-    exec u:r:tzdatacheck:s0 system system -- /system/bin/tzdatacheck /system/usr/share/zoneinfo /data/misc/zoneinfo
+    exec - system system -- /system/bin/tzdatacheck /system/usr/share/zoneinfo /data/misc/zoneinfo
 
     # If there is no fs-post-data action in the init.<device>.rc file, you
     # must uncomment this line, otherwise encrypted filesystems