OSDOCS-12711: Documented the balance-slb mode for networking docs

Author: dfitzmau

installing/installing_bare_metal/upi/installing-bare-metal-network-customizations.adoc

@@ -69,6 +69,9 @@ include::modules/installation-load-balancing-user-infra.adoc[leveloffset=+2]
 // Creating a manifest object that includes a customized `br-ex` bridge
 include::modules/creating-manifest-file-customized-br-ex-bridge.adoc[leveloffset=+1]
 
+// Enabling OVS balance-slb mode for your cluster
+include::modules/enabling- OVS-balance-slb-mode.adoc[leveloffset=+1]
+
 // Scale each machine set to compute nodes
 include::modules/creating-scaling-machine-sets-compute-nodes-networking.adoc[leveloffset=+2]