Don't run mbox reset until dbus object available

The mbox reset command run within this service requires the
mboxd dbus object (org.openbmc.mbox) be available. Prior to this
commit, OpenBMC tended to get lucky with the ordering but there
was no guarantee. This commit will ensure the ordering is
always right.

Resolves openbmc/openbmc#2850

Change-Id: Ia9efeb6e06ac47018d449ee2cab2651bc00ab0ed
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/meta-phosphor/common/recipes-phosphor/mboxd/mboxd/mboxd-reload@.service b/meta-phosphor/common/recipes-phosphor/mboxd/mboxd/mboxd-reload@.service
index 7fb2a5b..be02c7a 100644
--- a/meta-phosphor/common/recipes-phosphor/mboxd/mboxd/mboxd-reload@.service
+++ b/meta-phosphor/common/recipes-phosphor/mboxd/mboxd/mboxd-reload@.service
@@ -2,6 +2,8 @@
 Description=Reload mboxd during power on
 Wants=obmc-power-start-pre@%i.target
 Before=obmc-power-start-pre@%i.target
+Wants=mapper-wait@-org-openbmc-mboxd.service
+After=mapper-wait@-org-openbmc-mboxd.service
 Conflicts=obmc-chassis-poweroff@%i.target
 
 [Service]