[shill] Get rid of protected data members in PropertyStoreTest

BUG=chromium-os:19573
TEST=unit
STATUS=Verified

Change-Id: Ib3a2f19abb8cc4aa0e8410fc26bbb60891e35da7
Reviewed-on: http://gerrit.chromium.org/gerrit/7762
Tested-by: Chris Masone <cmasone@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
diff --git a/wifi_unittest.cc b/wifi_unittest.cc
index 3ffb266..adbb2e2 100644
--- a/wifi_unittest.cc
+++ b/wifi_unittest.cc
@@ -51,7 +51,7 @@
 class WiFiPropertyTest : public PropertyStoreTest {
  public:
   WiFiPropertyTest()
-      : device_(new WiFi(&control_interface_, NULL, NULL, "wifi", "", 0)) {
+      : device_(new WiFi(control_interface(), NULL, NULL, "wifi", "", 0)) {
   }
   virtual ~WiFiPropertyTest() {}