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/zip2zip/zip2zip_test.go

@@ -416,7 +416,6 @@ func errorString(e error) string {
 }
 
 func TestZip2Zip(t *testing.T) {
-	t.Parallel()
 	for _, testCase := range testCases {
 		t.Run(testCase.name, func(t *testing.T) {
 			inputBuf := &bytes.Buffer{}
@@ -473,7 +472,6 @@ func TestZip2Zip(t *testing.T) {
 }
 
 func TestConstantPartOfPattern(t *testing.T) {
-	t.Parallel()
 	testCases := []struct{ in, out string }{
 		{
 			in:  "",