Revert "Make lots of tests run in parallel"

This reverts commit 323dc60712.

Reason for revert: Possible cause of test instability
Bug: 170513220
Test: soong tests

Change-Id: Iee168e9fbb4210569e6cffcc23e60d111403abb8

python/python_test.go

@@ -326,7 +326,6 @@ var (
 )
 
 func TestPythonModule(t *testing.T) {
-	t.Parallel()
 	for _, d := range data {
 		t.Run(d.desc, func(t *testing.T) {
 			config := android.TestConfig(buildDir, nil, "", d.mockFiles)