Move ParseConnection*() to connection_utils.

We don't need real_shill_provider if USE_DBUS is 0, but we still need
these functions, and they have a duplicate copy in connection_manager,
so put them in utils and deduplicate.

Also moved StringForConnectionType() to connection_utils.

Bug: 28800946
Test: mma

Change-Id: If535fdc52bc8fb267921bea02b31d8d6580d5d54
diff --git a/mock_connection_manager.h b/mock_connection_manager.h
index 109c529..e37460b 100644
--- a/mock_connection_manager.h
+++ b/mock_connection_manager.h
@@ -31,11 +31,11 @@
   MockConnectionManager() = default;
 
   MOCK_METHOD2(GetConnectionProperties,
-               bool(NetworkConnectionType* out_type,
-                    NetworkTethering* out_tethering));
+               bool(ConnectionType* out_type,
+                    ConnectionTethering* out_tethering));
 
-  MOCK_CONST_METHOD2(IsUpdateAllowedOver, bool(NetworkConnectionType type,
-                                               NetworkTethering tethering));
+  MOCK_CONST_METHOD2(IsUpdateAllowedOver,
+                     bool(ConnectionType type, ConnectionTethering tethering));
 };
 
 }  // namespace chromeos_update_engine