meta-bletchley: motor-ctrl: fix host-ac-on failed during bmc boot

1. add service dependency to avoid host-ac-on service failed due to
inventory (presence_sledX) property not avaliable.

host-ac-on@X.service
  |- motor-init-calibration@X.service (Requires, After)
     |- phosphor-gpio-presence@presence-sledX.service (Requires, After)

2. simplify check method for ac-on & ac-off actions, just check host
ac status before set ac on/off.

3. fix host-ac-on service shows failed when ac is aready turned on
(ex: BMC reset), return 0 for both ac-on & ac-off actions no
matter GPIO (power-hostX) set required or not.

Signed-off-by: Potin Lai <potin.lai@quantatw.com>
Change-Id: I2c878dea05ea2511e6564c0980ba34dc28a46e2c
diff --git a/meta-facebook/meta-bletchley/recipes-bletchley/motor-ctrl/files/host-poweroff@.service b/meta-facebook/meta-bletchley/recipes-bletchley/motor-ctrl/files/host-poweroff@.service
index 50cd532..c81f6d6 100644
--- a/meta-facebook/meta-bletchley/recipes-bletchley/motor-ctrl/files/host-poweroff@.service
+++ b/meta-facebook/meta-bletchley/recipes-bletchley/motor-ctrl/files/host-poweroff@.service
@@ -2,6 +2,7 @@
 Description=Power off System in Sled%i by Step Motor
 Requires=motor-init-calibration@%i.service
 After=motor-init-calibration@%i.service
+Conflicts=host-poweron@%i.service
 
 [Service]
 Type=oneshot