apmanager: support on-demand device enumeration

Enumerate a new device when a new interface is detected but its
corresponding device has not been enumerated yet. This is possible
if apmanager starts before WiFi driver is loaded or a WiFi device
is plug-in during run time.

BUG=chromium:431763
TEST=unittests

Change-Id: I9df224ae8ed55f50d629c4386088c508ebffb223
Reviewed-on: https://chromium-review.googlesource.com/231476
Reviewed-by: Peter Qiu <zqiu@chromium.org>
Commit-Queue: Peter Qiu <zqiu@chromium.org>
Tested-by: Peter Qiu <zqiu@chromium.org>
diff --git a/mock_device.h b/mock_device.h
index 2f0ee53..8696681 100644
--- a/mock_device.h
+++ b/mock_device.h
@@ -23,7 +23,7 @@
                void(const WiFiInterface& interface));
   MOCK_METHOD1(DeregisterInterface,
                void(const WiFiInterface& interface));
-  MOCK_METHOD1(ParseWiFiPhyInfo,
+  MOCK_METHOD1(ParseWiphyCapability,
                void(const shill::Nl80211Message& msg));
   MOCK_METHOD0(ClaimDevice, bool());
   MOCK_METHOD0(ReleaseDevice, bool());