Add "after" PowerSupplyRedundancy mapper object

The org.openbmc.Sensors.service reads the value of
/xyz/openbmc_project/control/power_supply_redundancy
when starting to determine the value of
/xyz/openbmc_project/sensors/chassis/PowerSupplyRedundancy.
This happens in sensors.py.

Change-Id: If594a4986ebffd0811a8a76002739bd0022ca767
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/meta-phosphor/common/recipes-phosphor/sensors/obmc-mgr-sensor/org.openbmc.Sensors.service b/meta-phosphor/common/recipes-phosphor/sensors/obmc-mgr-sensor/org.openbmc.Sensors.service
index b9da01e..cc59338 100644
--- a/meta-phosphor/common/recipes-phosphor/sensors/obmc-mgr-sensor/org.openbmc.Sensors.service
+++ b/meta-phosphor/common/recipes-phosphor/sensors/obmc-mgr-sensor/org.openbmc.Sensors.service
@@ -1,5 +1,7 @@
 [Unit]
 Description=Phosphor Sensor Manager
+Wants=mapper-wait@-xyz-openbmc_project-control-power_supply_redundancy.service
+After=mapper-wait@-xyz-openbmc_project-control-power_supply_redundancy.service
 
 [Service]
 Restart=always