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/omaha_request_action_unittest.cc b/omaha_request_action_unittest.cc
index d4b166f..82f9ae8 100644
--- a/omaha_request_action_unittest.cc
+++ b/omaha_request_action_unittest.cc
@@ -467,11 +467,11 @@
 
   EXPECT_CALL(mock_cm, GetConnectionProperties(_, _))
       .WillRepeatedly(
-          DoAll(SetArgumentPointee<0>(NetworkConnectionType::kEthernet),
-                SetArgumentPointee<1>(NetworkTethering::kUnknown),
+          DoAll(SetArgumentPointee<0>(ConnectionType::kEthernet),
+                SetArgumentPointee<1>(ConnectionTethering::kUnknown),
                 Return(true)));
-  EXPECT_CALL(mock_cm, IsUpdateAllowedOver(NetworkConnectionType::kEthernet, _))
-    .WillRepeatedly(Return(false));
+  EXPECT_CALL(mock_cm, IsUpdateAllowedOver(ConnectionType::kEthernet, _))
+      .WillRepeatedly(Return(false));
 
   ASSERT_FALSE(
       TestUpdateCheck(nullptr,  // request_params