NFSv4: Let CLAIM_PREVIOUS close the file immediately

There is no need to use 'll' (type 'leavesToClose') here, as we're not
operating under any locks. It's perfectly fine to call into the VFS
directly.

pkg/filesystem/virtual/nfsv4/base_program.go

@@ -1714,7 +1714,7 @@ func (s *compoundState) txOpen(ctx context.Context, args *nfsv4.Open4args, oos *
 		); vs != virtual.StatusOK {
 			return &nfsv4.Open4res_default{Status: toNFSv4Status(vs)}
 		}
-		ll.leaves = append(ll.leaves, currentLeaf)
+		currentLeaf.VirtualClose()
 
 		p.enter()
 		isLocked = true

pkg/filesystem/virtual/nfsv4/base_program_test.go

@@ -3052,8 +3052,8 @@ func TestBaseProgramCompound_OP_OPEN(t *testing.T) {
 			clock.EXPECT().Now().Return(time.Unix(1019, 0))
 			clock.EXPECT().Now().Return(time.Unix(1020, 0))
 			leaf.EXPECT().VirtualOpenSelf(ctx, virtual.ShareMaskRead, &virtual.OpenExistingOptions{}, virtual.AttributesMask(0), gomock.Any())
-			clock.EXPECT().Now().Return(time.Unix(1021, 0))
 			leaf.EXPECT().VirtualClose()
+			clock.EXPECT().Now().Return(time.Unix(1021, 0))
 
 			res, err := program.NfsV4Nfsproc4Compound(ctx, &nfsv4_xdr.Compound4args{
 				Tag: "open",