limayaml/defaults_test.go: fix incorrect expect.Mounts[0].Virtiofs.QueueSize

`expect.Mounts[0]` was the same instance as each of `y.Mounts[0]` and `d.Mounts[0]`, so the test passed regardless of the value set for `Virtiofs.QueueSize`.
The default for `Virtiofs.QueueSize` is `nil`, but I'll keep the code that explicitly sets it to `nil` to make it clear that `nil` is expected.

Signed-off-by: Norio Nomura <norio.nomura@gmail.com>

Author: norio-nomura

pkg/limayaml/defaults_test.go

@@ -212,7 +212,7 @@ func TestFillDefault(t *testing.T) {
 	expect.Mounts[0].NineP.ProtocolVersion = ptr.Of(Default9pProtocolVersion)
 	expect.Mounts[0].NineP.Msize = ptr.Of(Default9pMsize)
 	expect.Mounts[0].NineP.Cache = ptr.Of(Default9pCacheForRO)
-	expect.Mounts[0].Virtiofs.QueueSize = ptr.Of(DefaultVirtiofsQueueSize)
+	expect.Mounts[0].Virtiofs.QueueSize = nil
 	// Only missing Mounts field is Writable, and the default value is also the null value: false
 
 	expect.MountType = ptr.Of(NINEP)
@@ -423,7 +423,7 @@ func TestFillDefault(t *testing.T) {
 	expect.Mounts[0].NineP.ProtocolVersion = ptr.Of(Default9pProtocolVersion)
 	expect.Mounts[0].NineP.Msize = ptr.Of(Default9pMsize)
 	expect.Mounts[0].NineP.Cache = ptr.Of(Default9pCacheForRO)
-	expect.Mounts[0].Virtiofs.QueueSize = ptr.Of(DefaultVirtiofsQueueSize)
+	expect.Mounts[0].Virtiofs.QueueSize = nil
 	expect.HostResolver.Hosts = map[string]string{
 		"default": d.HostResolver.Hosts["default"],
 	}