tss: Correct home directory to /var/lib/tpm.

Trousers makes use of its home directory so this cannot be /dev/null and
users.eclass is being updated to fail if the homedir argument to
enewuser is set since it should be defined here.

BUG=chromium:933582
TEST=PreCQ passes

Change-Id: I3f4ee3b6034e5e2438cf12c79d9f9dc403617970
Reviewed-on: https://chromium-review.googlesource.com/1492494
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

profiles/base/accounts/user/tss

diff --git a/profiles/base/accounts/user/tss b/profiles/base/accounts/user/tss
index 5af1004..ca12f83 100644
--- a/profiles/base/accounts/user/tss
+++ b/profiles/base/accounts/user/tss
@@ -2,5 +2,5 @@
 uid:207
 gid:207
 gecos:trousers, TPM and TSS operations
-home:/dev/null
+home:/var/lib/tpm
 shell:/bin/false