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

cmd/javac_wrapper/javac_wrapper_test.go

@@ -93,7 +93,6 @@ warning: [options] bootstrap class path not set in conjunction with -source 1.9\
 }
 
 func TestJavacColorize(t *testing.T) {
-	t.Parallel()
 	for i, test := range testCases {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			buf := new(bytes.Buffer)
@@ -111,7 +110,6 @@ func TestJavacColorize(t *testing.T) {
 }
 
 func TestSubprocess(t *testing.T) {
-	t.Parallel()
 	t.Run("failure", func(t *testing.T) {
 		exitCode, err := Main(ioutil.Discard, "test", []string{"sh", "-c", "exit 9"})
 		if err != nil {