Fix Remove-AzureAvailabilitySet issue

Author: hyonholee

src/ServiceManagement/Compute/Commands.ServiceManagement.Test/FunctionalTests/FunctionalTest.cs

@@ -280,21 +280,13 @@ public void AzureAvailabilitySetTest()
                 vmPowershellCmdlets.UpdateAzureVM(vmName, serviceName, vm);
                 Assert.IsTrue(Verify.AzureAvailabilitySet(vmPowershellCmdlets.GetAzureVM(vmName, serviceName).VM, testAVSetName));
 
-                vm = vmPowershellCmdlets.SetAzureAvailabilitySet(vmName, serviceName, string.Empty);
-                vmPowershellCmdlets.UpdateAzureVM(vmName, serviceName, vm);
-                Assert.IsTrue(Verify.AzureAvailabilitySet(vmPowershellCmdlets.GetAzureVM(vmName, serviceName).VM, string.Empty));
-
-                vm = vmPowershellCmdlets.SetAzureAvailabilitySet(vmName, serviceName, testAVSetName);
-                vmPowershellCmdlets.UpdateAzureVM(vmName, serviceName, vm);
-                Assert.IsTrue(Verify.AzureAvailabilitySet(vmPowershellCmdlets.GetAzureVM(vmName, serviceName).VM, testAVSetName));
-
                 vm = vmPowershellCmdlets.SetAzureAvailabilitySet(vmName, serviceName, null);
                 vmPowershellCmdlets.UpdateAzureVM(vmName, serviceName, vm);
                 Assert.IsTrue(Verify.AzureAvailabilitySet(vmPowershellCmdlets.GetAzureVM(vmName, serviceName).VM, testAVSetName));
 
                 vm = vmPowershellCmdlets.RemoveAzureAvailabilitySet(vmName, serviceName);
                 vmPowershellCmdlets.UpdateAzureVM(vmName, serviceName, vm);
-                Assert.IsTrue(Verify.AzureAvailabilitySet(vmPowershellCmdlets.GetAzureVM(vmName, serviceName).VM, testAVSetName));
+                Assert.IsTrue(Verify.AzureAvailabilitySet(vmPowershellCmdlets.GetAzureVM(vmName, serviceName).VM, null));
 
                 pass = true;
             }

src/ServiceManagement/Compute/Commands.ServiceManagement/IaaS/AvailabilitySets/RemoveAzureAvailabilitySet.cs

@@ -23,7 +23,7 @@ public class RemoveAzureAvailabilitySet : VirtualMachineConfigurationCmdletBase
         protected override void ProcessRecord()
         {
             base.ProcessRecord();
-            this.VM.GetInstance().AvailabilitySetName = null;
+            this.VM.GetInstance().AvailabilitySetName = string.Empty;
             this.WriteObject(this.VM, true);
         }
     }