Recipe update: User management, systemd patch, IPMI net functions

Create virtual class to include user management in the image
Add the systemd patch for network support to the systemd recipe
Update the IPMI recipe to pickup the support for network configuration
diff --git a/conf/machine/include/sample.inc b/conf/machine/include/sample.inc
index f6fe46d..e66dc77 100644
--- a/conf/machine/include/sample.inc
+++ b/conf/machine/include/sample.inc
@@ -30,3 +30,4 @@
 PREFERRED_PROVIDER_virtual/obmc-phosphor-policy-mgmt = "obmc-phosphor-policyd"
 PREFERRED_PROVIDER_virtual/obmc-phosphor-sensor-mgmt = "obmc-phosphor-sensord"
 PREFERRED_PROVIDER_virtual/obmc-phosphor-system-mgmt = "obmc-phosphor-sysd"
+PREFERRED_PROVIDER_virtual/obmc-phosphor-user-mgmt = "obmc-phosphor-userd"