Make lots of tests run in parallel

Putting t.Parallel() in each test makes them run in parallel.
Additional t.Parallel() could be added to each subtest, although
that requires making a local copy of the loop variable for
table driven tests.

Test: m checkbuild
Change-Id: I5d9869ead441093f4d7c5757f2447385333a95a4

android/defaults_test.go

@@ -59,6 +59,7 @@ func defaultsTestDefaultsFactory() Module {
 }
 
 func TestDefaults(t *testing.T) {
+	t.Parallel()
 	bp := `
 		defaults {
 			name: "transitive",
@@ -102,6 +103,7 @@ func TestDefaults(t *testing.T) {
 }
 
 func TestDefaultsAllowMissingDependencies(t *testing.T) {
+	t.Parallel()
 	bp := `
 		defaults {
 			name: "defaults",