update configuring_bridge

Added EDGE per https://eucalyptus.atlassian.net/browse/DOC-1397

Author: jkomg

content/en_us/install-guide/configuring_bridge_ha.dita

@@ -3,7 +3,7 @@
 <!DOCTYPE task PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">
 <task id="configuring_bridge_ha">
 	<title>Configure Bridges</title>
-	<shortdesc>For Managed (No VLAN) mode, you must configure a Linux ethernet bridge on all NC
+	<shortdesc>For Managed (No VLAN) and EDGE modes, you must configure a Linux ethernet bridge on all NC
 		machines. This bridge connects your local ethernet adapter to the cluster network. Under
 		normal operation, NCs will attach virtual machine instances to this bridge when the
 		instances are booted. </shortdesc>