shill: rtnl: Handle setting of peer address

Bonus changes: Rename "subnet_cidr" to "subnet_prefix".  Set a default
subnet prefix for OpenVPNDriver IPConfigs.

BUG=chromium-os:28003
TEST=Unit tests.

Change-Id: I953748b3ecb1a45237cedc18482c647eebe27efa
Reviewed-on: https://gerrit.chromium.org/gerrit/18461
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
diff --git a/connection_unittest.cc b/connection_unittest.cc
index 728f347..0aeae1e 100644
--- a/connection_unittest.cc
+++ b/connection_unittest.cc
@@ -104,7 +104,7 @@
 
 TEST_F(ConnectionTest, AddConfig) {
   EXPECT_CALL(rtnl_handler_,
-              AddInterfaceAddress(kTestDeviceInterfaceIndex0, _, _));
+              AddInterfaceAddress(kTestDeviceInterfaceIndex0, _, _, _));
   EXPECT_CALL(routing_table_,
               SetDefaultRoute(kTestDeviceInterfaceIndex0,
                               ipconfig_,
@@ -165,7 +165,7 @@
   connection_->SetIsDefault(true);
 
   EXPECT_CALL(rtnl_handler_,
-              AddInterfaceAddress(kTestDeviceInterfaceIndex0, _, _));
+              AddInterfaceAddress(kTestDeviceInterfaceIndex0, _, _, _));
   EXPECT_CALL(routing_table_, SetDefaultRoute(kTestDeviceInterfaceIndex0,
                                              ipconfig_,
                                              Connection::kDefaultMetric));