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

partner/androidmk/androidmk_test.go

@@ -54,6 +54,7 @@ cc_library_shared {
 }
 
 func TestEndToEnd(t *testing.T) {
+	t.Parallel()
 	for i, test := range testCases {
 		expected, err := bpfix.Reformat(test.expected)
 		if err != nil {