shill: set ethernet_service signal strength to max. (so if it has to
compete with wifi_service, it isn't unfairly penalized.)

BUG=chromium-os:26529
TEST=unit tests

Collateral change: update WiFiService (and its unit tests) to
use Service::kStrengthMin and Service::kStrengthMax.

Change-Id: I208fd2ce7a8dba8dbd6c72ae2f8fdd8b90ed9c12
Reviewed-on: https://gerrit.chromium.org/gerrit/16403
Commit-Ready: mukesh agrawal <quiche@chromium.org>
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
diff --git a/ethernet_service.cc b/ethernet_service.cc
index d67adae..dda7e1b 100644
--- a/ethernet_service.cc
+++ b/ethernet_service.cc
@@ -41,6 +41,7 @@
   set_connectable(true);
   set_auto_connect(true);
   set_friendly_name(GetStorageIdentifier());
+  SetStrength(kStrengthMax);
 }
 
 EthernetService::~EthernetService() { }