systemd: Save random seed during powercycle

This allows us to better keep track of the last system time and
randomness information during subsequent "reboots".

Change-Id: I80235e6af2f87b9a28e6052f6890d6288f03d632
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/gbmc-psu-hardreset.target b/gbmc-psu-hardreset.target
index 4b9133d..4fd706a 100644
--- a/gbmc-psu-hardreset.target
+++ b/gbmc-psu-hardreset.target
@@ -3,3 +3,5 @@
 StopWhenUnneeded=true
 Wants=gbmc-psu-hardreset-pre.target
 After=gbmc-psu-hardreset-pre.target
+Conflicts=systemd-random-seed.service
+After=systemd-random-seed.service