fix: govc vm.destroy only destroys the 1st argument

With PR #2532 , vm.destroy was returning after the 1st VM was destroyed.

Author: dougm

govc/test/vm.bats

@@ -319,6 +319,12 @@ load test_helper
   # destroy powers off vm before destruction
   run govc vm.destroy $vm
   assert_success
+
+  run govc vm.destroy '*'
+  assert_success
+
+  run govc find / -type m
+  assert_success "" # expect all VMs are gone
 }
 
 @test "vm.create pvscsi" {

govc/vm/destroy.go

@@ -101,7 +101,9 @@ func (cmd *destroy) Run(ctx context.Context, f *flag.FlagSet) error {
 			return err
 		}
 
-		return task.Wait(ctx)
+		if err = task.Wait(ctx); err != nil {
+			return err
+		}
 	}
 
 	return nil