dbus-monitor: add dependency on snmp service

All IBM systems support the SNMP trap notification for error logs. This
means phosphor-dbus-monitor needs to be careful to not start until the
SNMP service is up and running.

Without this dependency, situations can be hit, when lots of errors are
present, where the phosphor-dbus-monitor calls into the SNMP shared
library and hits an unhandled exception when trying to talk to the SNMP
service.

Tested:
- Verified the unhandled exception is no longer seen and
  phosphor-dbus-monitor starts after the SNMP service.

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I8b4ca94c0cdd7721aa8847dc478f3827f040a654
diff --git a/meta-ibm/recipes-phosphor/dbus/phosphor-dbus-monitor/phosphor-dbus-monitor-snmp.conf b/meta-ibm/recipes-phosphor/dbus/phosphor-dbus-monitor/phosphor-dbus-monitor-snmp.conf
new file mode 100644
index 0000000..6b4f7f5
--- /dev/null
+++ b/meta-ibm/recipes-phosphor/dbus/phosphor-dbus-monitor/phosphor-dbus-monitor-snmp.conf
@@ -0,0 +1,3 @@
+[Unit]
+Wants=mapper-wait@-xyz-openbmc_project-network-snmp.service
+After=mapper-wait@-xyz-openbmc_project-network-snmp.service
diff --git a/meta-ibm/recipes-phosphor/dbus/phosphor-dbus-monitor_%.bbappend b/meta-ibm/recipes-phosphor/dbus/phosphor-dbus-monitor_%.bbappend
index 6731a7a..78d2d49 100644
--- a/meta-ibm/recipes-phosphor/dbus/phosphor-dbus-monitor_%.bbappend
+++ b/meta-ibm/recipes-phosphor/dbus/phosphor-dbus-monitor_%.bbappend
@@ -1,2 +1,5 @@
+FILESEXTRAPATHS:prepend := "${THISDIR}/${BPN}:"
+
 SYSTEMD_LINK:phosphor-msl-verify:append:ibm-ac-server = " ../phosphor-msl-verify.service:obmc-chassis-poweron@0.target.requires/phosphor-msl-verify.service"
 SYSTEMD_LINK:phosphor-msl-verify:append:mihawk = " ../phosphor-msl-verify.service:obmc-chassis-poweron@0.target.requires/phosphor-msl-verify.service"
+SYSTEMD_OVERRIDE:${PN}:append = " phosphor-dbus-monitor-snmp.conf:phosphor-dbus-monitor.service.d/phosphor-dbus-monitor-snmp.conf"