shill: connection: Allow missing broadcast

Teunnel interfaces do not have a broadcast address since they
are p-t-p.  Hand the Connection object a technology identifier
so it can make such decisions.  We may need to explore polymorphism
in the future if decisions of this sort become more prevalent.

BUG=chromium-os:27929
TEST=Unit tests

Change-Id: I1a81d010c60319015bf0ac690baf3edb62a39cdf
Reviewed-on: https://gerrit.chromium.org/gerrit/18361
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
diff --git a/mock_connection.cc b/mock_connection.cc
index 6715994..4648fa4 100644
--- a/mock_connection.cc
+++ b/mock_connection.cc
@@ -9,7 +9,7 @@
 namespace shill {
 
 MockConnection::MockConnection(const DeviceInfo *device_info)
-    : Connection(0, std::string(), device_info) {}
+    : Connection(0, std::string(), Technology::kUnknown, device_info) {}
 
 MockConnection::~MockConnection() {}