Fix a bug in driving LED during PowerOn and PowerOff

As part of PowerOn, group 'power_on' gets asserted via
a service file that is associated with PowerOn and that
results in driving corresponding physical LEDs.

This works fine for a single PowerOn and does not work if
there is a PowerOff followed by a PowerOn.

Service file had RemainAfterExit set and did not have a stop
condition. This commit puts a Conflicts relationship with
appropriate stop service file and vice versa.

Fixes openbmc/openbmc#1918

Change-Id: Ie0e6b554b3ab7beacd3ad15a0ff76e4d6481f648
Signed-off-by: Vishwanatha Subbanna <vishwa@linux.vnet.ibm.com>
diff --git a/common/recipes-phosphor/leds/phosphor-led-manager/obmc-led-group-stop@.service b/common/recipes-phosphor/leds/phosphor-led-manager/obmc-led-group-stop@.service
index 4ddf0f8..e7799f3 100644
--- a/common/recipes-phosphor/leds/phosphor-led-manager/obmc-led-group-stop@.service
+++ b/common/recipes-phosphor/leds/phosphor-led-manager/obmc-led-group-stop@.service
@@ -2,6 +2,7 @@
 Description=Assert %i LED
 Wants=mapper-wait@-xyz-openbmc_project-led-groups-%i.service
 After=mapper-wait@-xyz-openbmc_project-led-groups-%i.service
+Conflicts=obmc-led-group-start@%i.service
 
 [Service]
 Type=oneshot