nobody: Change homedir to /dev/null

/var/empty is being migrated to /mnt/empty, but in this case /dev/null
was used for consistency.

CQ-DEPEND=CL:1489552,CL:*903550,CL:*903551
BUG=chromium:933582
TEST=build_packages, build_image, ssh into test machine, PreCQ passes.

Change-Id: I768b7c89c117de2fc081629f6ba8cd6075b9c72e
Reviewed-on: https://chromium-review.googlesource.com/1489186
Commit-Ready: Allen Webb <allenwebb@google.com>
Tested-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/profiles/base/accounts/user/nobody b/profiles/base/accounts/user/nobody
index 43b3d7a..fe75a84 100644
--- a/profiles/base/accounts/user/nobody
+++ b/profiles/base/accounts/user/nobody
@@ -2,5 +2,5 @@
 uid:65534
 gid:65534
 gecos:nobody
-home:/var/empty
+home:/dev/null
 shell:/bin/false