tlsdate: Adding systemd service file.

BUG=chromium:583671
CQ-DEPEND=CL:375878
TEST=Checked that the service runs.

Change-Id: I770b9b32cb81a121aca0cbd69cad8b130183db84
Reviewed-on: https://chromium-review.googlesource.com/375898
Commit-Ready: Sabin Flo <sabin.floares@gmail.com>
Tested-by: Sabin Flo <sabin.floares@gmail.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
2 files changed