Fix ConnectionTypeToString unittest.

We removed ConnectionTypeToString() to use StringForConnectionType() instead,
but it's using constants from shill:: which is lowercase.

Bug: 28800946
Test: ./update_engine_unittests

Change-Id: Ic276b7bc8e4529b04373adefeef7503f9fb0efd2
diff --git a/update_manager/boxed_value_unittest.cc b/update_manager/boxed_value_unittest.cc
index 3d0c72e..2a086a6 100644
--- a/update_manager/boxed_value_unittest.cc
+++ b/update_manager/boxed_value_unittest.cc
@@ -158,17 +158,17 @@
 }
 
 TEST(UmBoxedValueTest, ConnectionTypeToString) {
-  EXPECT_EQ("Ethernet",
+  EXPECT_EQ("ethernet",
             BoxedValue(new ConnectionType(ConnectionType::kEthernet))
             .ToString());
-  EXPECT_EQ("Wifi",
+  EXPECT_EQ("wifi",
             BoxedValue(new ConnectionType(ConnectionType::kWifi)).ToString());
-  EXPECT_EQ("Wimax",
+  EXPECT_EQ("wimax",
             BoxedValue(new ConnectionType(ConnectionType::kWimax)).ToString());
-  EXPECT_EQ("Bluetooth",
+  EXPECT_EQ("bluetooth",
             BoxedValue(new ConnectionType(ConnectionType::kBluetooth))
             .ToString());
-  EXPECT_EQ("Cellular",
+  EXPECT_EQ("cellular",
             BoxedValue(new ConnectionType(ConnectionType::kCellular))
             .ToString());
   EXPECT_EQ("Unknown",
@@ -195,11 +195,11 @@
   set<ConnectionType>* set1 = new set<ConnectionType>;
   set1->insert(ConnectionType::kWimax);
   set1->insert(ConnectionType::kEthernet);
-  EXPECT_EQ("Ethernet,Wimax", BoxedValue(set1).ToString());
+  EXPECT_EQ("ethernet,wimax", BoxedValue(set1).ToString());
 
   set<ConnectionType>* set2 = new set<ConnectionType>;
   set2->insert(ConnectionType::kWifi);
-  EXPECT_EQ("Wifi", BoxedValue(set2).ToString());
+  EXPECT_EQ("wifi", BoxedValue(set2).ToString());
 }
 
 TEST(UmBoxedValueTest, StageToString) {