Remove gmock from managed_network_configuration_handler_unittest.cc part 1.

This has following two changes.
- Rename ManagedNetworkConfigurationHandlerTest to
  ManagedNetworkConfigurationHandlerMockTest, and then deprecate it.
- Introduce a new ManagedNetworkConfigurationHandlerTest test fixture,
  which uses Fake implementation instead of gmock.
- Migrated four tests using policy/shill_policy_on_unconfigured_wifi1.json
  into new test fixture.

BUG=234463
TEST=Ran bots.

Change-Id: I50114a323605eafd9e67accb1232c72783d3c572
Reviewed-on: https://chromium-review.googlesource.com/766407
Commit-Queue: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516327}

chromeos/network/managed_network_configuration_handler_impl.h

@@ -116,6 +116,7 @@ class CHROMEOS_EXPORT ManagedNetworkConfigurationHandlerImpl
   friend class AutoConnectHandlerTest;
   friend class ClientCertResolverTest;
   friend class ManagedNetworkConfigurationHandlerTest;
+  friend class ManagedNetworkConfigurationHandlerMockTest;
   friend class NetworkConnectionHandlerImplTest;
   friend class NetworkHandler;
   friend class ProhibitedTechnologiesHandlerTest;

chromeos/test/data/network/policy/shill_policy_on_unconfigured_wifi1.json

 {
+  "Device": "/device/wifi1",
   "GUID": "policy_wifi1",
   "Mode": "managed",
+  "Name": "policy_wifi1",
   "Passphrase": "policy's passphrase",
   "Profile": "/profile/user1/shill",
+  "SSID": "policy_wifi1",
   "SecurityClass": "psk",
+  "State": "idle",
   "Type": "wifi",
   "UIData": "{\"onc_source\":\"user_policy\"}",
+  "Visible": true,
   "WiFi.HexSSID": "7769666931"  // "wifi1"
 }