Fix loop-closure bugs in tests

...which were flagged by golangci-lint v1.51.

Signed-off-by: Cory Snider <csnider@mirantis.com>

distribution/xfer/download_test.go

@@ -389,6 +389,7 @@ func TestMaxDownloadAttempts(t *testing.T) {
 		},
 	}
 	for _, tc := range tests {
+		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 			layerStore := &mockLayerStore{make(map[layer.ChainID]*mockLayer)}

integration/build/build_test.go

@@ -90,6 +90,7 @@ func TestBuildWithRemoveAndForceRemove(t *testing.T) {
 	client := testEnv.APIClient()
 	ctx := context.Background()
 	for _, c := range cases {
+		c := c
 		t.Run(c.name, func(t *testing.T) {
 			t.Parallel()
 			dockerfile := []byte(c.dockerfile)