Added validate set for plan

Author: safeermohammed

src/ResourceManager/Automation/Commands.Automation/Cmdlet/NewAzureAutomationAccount.cs

@@ -75,6 +75,7 @@ public IAutomationClient AutomationClient
         /// Gets or sets the plan.
         /// </summary>
         [Parameter( Mandatory = false, ValueFromPipelineByPropertyName = true, HelpMessage = "The plan of the automation account")]
+        [ValidateSet("Free", "Basic", IgnoreCase = true)]
         public string Plan { get; set; }
 
         /// <summary>

src/ResourceManager/Automation/Commands.Automation/Cmdlet/SetAzureAutomationAccount.cs

@@ -69,6 +69,7 @@ public IAutomationClient AutomationClient
         /// Gets or sets the plan.
         /// </summary>
         [Parameter( Mandatory = false, ValueFromPipelineByPropertyName = true, HelpMessage = "The plan of the automation account")]
+        [ValidateSet("Free", "Basic", IgnoreCase = true)]
         public string Plan { get; set; }
 
         /// <summary>