Stop installing the sync user

We don't even know what this is used for.

CQ-DEPEND=CL:203775
BUG=chromium:362216
TEST=security_AccountsBaseline
TEST=paladin trybot

Change-Id: I02aa0ffa91a6f7de8a15d2d4b7ab4d027408bf53
Reviewed-on: https://chromium-review.googlesource.com/203942
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>
Commit-Queue: Chris Masone <cmasone@chromium.org>
diff --git a/profiles/base/accounts/user/sync b/profiles/base/accounts/user/sync
index 5e59da0..8ca39bc 100644
--- a/profiles/base/accounts/user/sync
+++ b/profiles/base/accounts/user/sync
@@ -4,3 +4,4 @@
 gecos:sync
 home:/sbin
 shell:/bin/sync
+defunct:true