os: use different test files on android

Some Android OS installations have very strange permissions on their
/system/etc directory, meaning that Readdir fails. Instead use
/system/framework, which is far more regular.

Change-Id: Iefc140614183cda0f875e0f6ef859f4d4eaad9da
Reviewed-on: https://go-review.googlesource.com/17078Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/os/os_test.go

@@ -47,10 +47,10 @@ var sysdir = func() *sysDir {
 	switch runtime.GOOS {
 	case "android":
 		return &sysDir{
-			"/system/etc",
+			"/system/framework",
 			[]string{
-				"audio_policy.conf",
-				"system_fonts.xml",
+				"ext.jar",
+				"framework.jar",
 			},
 		}
 	case "darwin":