cleanup: address golangci 'usetesting' linter issues

When a context.Context is needed in a unit test, t.Context() should be
used instead of creating a new one with context.TODO() or
context.Background().

Signed-off-by: Niels de Vos <ndevos@ibm.com>

internal/rbd/nodeserver_test.go

@@ -17,7 +17,6 @@ limitations under the License.
 package rbd
 
 import (
-	"context"
 	"encoding/json"
 	"os"
 	"testing"
@@ -67,7 +66,7 @@ func TestGetStagingPath(t *testing.T) {
 
 func TestParseBoolOption(t *testing.T) {
 	t.Parallel()
-	ctx := context.TODO()
+	ctx := t.Context()
 	optionName := "myOption"
 	defaultValue := false