updated the api documentation for createNetworkOffering and updateNetworkOffering

api/src/main/java/org/apache/cloudstack/api/command/admin/network/CreateNetworkOfferingCmd.java

@@ -73,7 +73,8 @@ public class CreateNetworkOfferingCmd extends BaseCmd {
     @Parameter(name = ApiConstants.SPECIFY_VLAN, type = CommandType.BOOLEAN, description = "true if network offering supports vlans")
     private Boolean specifyVlan;
 
-    @Parameter(name = ApiConstants.AVAILABILITY, type = CommandType.STRING, description = "the availability of network offering. Default value is Optional")
+    @Parameter(name = ApiConstants.AVAILABILITY, type = CommandType.STRING, description = "the availability of network offering. The default value is Optional. "
+            + " Another value is Required, which will make it as the default network offering for new networks ")
     private String availability;
 
     @Parameter(name = ApiConstants.NETWORKRATE, type = CommandType.INTEGER, description = "data transfer rate in megabits per second allowed")

api/src/main/java/org/apache/cloudstack/api/command/admin/network/UpdateNetworkOfferingCmd.java

@@ -55,7 +55,7 @@ public class UpdateNetworkOfferingCmd extends BaseCmd {
     private String displayText;
 
     @Parameter(name = ApiConstants.AVAILABILITY, type = CommandType.STRING, description = "the availability of network offering."
-            + " Default value is Required for Guest Virtual network offering; Optional for Guest Direct network offering")
+            + " The value is Required makes this network offering default for Guest Virtual Networks. Only one network offering can have the value Required ")
     private String availability;
 
     @Parameter(name = ApiConstants.SORT_KEY, type = CommandType.INTEGER, description = "sort key of the network offering, integer")