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/neverallow_test.go

@@ -343,7 +343,6 @@ var neverallowTests = []struct {
 }
 
 func TestNeverallow(t *testing.T) {
-	t.Parallel()
 	for _, test := range neverallowTests {
 		// Create a test per config to allow for test specific config, e.g. test rules.
 		config := TestConfig(buildDir, nil, "", test.fs)