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
diff --git a/android/package_test.go b/android/package_test.go
index 04dfc08..a4b4c60 100644
--- a/android/package_test.go
+++ b/android/package_test.go
@@ -56,6 +56,7 @@
 }
 
 func TestPackage(t *testing.T) {
+	t.Parallel()
 	for _, test := range packageTests {
 		t.Run(test.name, func(t *testing.T) {
 			_, errs := testPackage(test.fs)