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

android/variable_test.go

@@ -112,7 +112,6 @@ var printfIntoPropertyTestCases = []printfIntoPropertyTestCase{
 }
 
 func TestPrintfIntoProperty(t *testing.T) {
-	t.Parallel()
 	for _, testCase := range printfIntoPropertyTestCases {
 		s := testCase.in
 		v := reflect.ValueOf(&s).Elem()
@@ -158,7 +157,6 @@ func testProductVariableModuleFactoryFactory(props interface{}) func() Module {
 }
 
 func TestProductVariables(t *testing.T) {
-	t.Parallel()
 	ctx := NewTestContext()
 	// A module type that has a srcs property but not a cflags property.
 	ctx.RegisterModuleType("module1", testProductVariableModuleFactoryFactory(&struct {
@@ -267,7 +265,6 @@ func productVariablesDefaultsTestDefaultsFactory() Module {
 
 // Test a defaults module that supports more product variable properties than the target module.
 func TestProductVariablesDefaults(t *testing.T) {
-	t.Parallel()
 	bp := `
 		defaults {
 			name: "defaults",