add bootlockboxd to tss

This CL adds bootlockboxd to tss group because bootlockboxd need
to access TPM.

BUG=b:67912719
CQ-DEPEND=CL:1000172
TEST=build image and tested bootlockbox daemon running as bootlockbox
user successefully sign and verify signatures.

Change-Id: I0dd85152f39733d0a641b1ff074649573f7317ad
Reviewed-on: https://chromium-review.googlesource.com/967255
Commit-Ready: Xiaoyong Zhou <xzhou@chromium.org>
Tested-by: Xiaoyong Zhou <xzhou@chromium.org>
Reviewed-by: Mattias Nissler <mnissler@chromium.org>
Reviewed-by: Andrey Pronin <apronin@chromium.org>
diff --git a/profiles/base/accounts/group/tss b/profiles/base/accounts/group/tss
index 65bff04..ba4fc11 100644
--- a/profiles/base/accounts/group/tss
+++ b/profiles/base/accounts/group/tss
@@ -1,4 +1,4 @@
 group:tss
 gid:207
 # Only certain users are allowed to talk to the TPM via tcsd.
-users:root,chaps,attestation,tpm_manager,trunks
+users:root,chaps,attestation,tpm_manager,trunks,bootlockboxd