shill: deviceinfo: Mark all loopback devices up

We largely ignore loopback interfaces, but mark the link up.

BUG=chromium-os:29334
TEST=New unit test plus test on machine by setting lo down and starting shill

Change-Id: I46b7eb21280ff88ed935b940273901f334b78c4e
Reviewed-on: https://gerrit.chromium.org/gerrit/20023
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
diff --git a/technology.h b/technology.h
index 781b1f5..d881481 100644
--- a/technology.h
+++ b/technology.h
@@ -24,6 +24,7 @@
     kVPN,
     kTunnel,
     kBlacklisted,
+    kLoopback,
     kUnknown,
   };
 
@@ -53,6 +54,7 @@
       Error *error);
 
  private:
+  static const char kLoopbackName[];
   static const char kTunnelName[];
   static const char kUnknownName[];
 };