shill: Add support for Cellular.SupportNetworkScan property.

BUG=chromium-os:25851
TEST=unit tests

Change-Id: Ie402be0144f6f8d408ebfd8d904044e7bd20e890
Reviewed-on: https://gerrit.chromium.org/gerrit/15225
Commit-Ready: Darin Petkov <petkov@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Darin Petkov <petkov@chromium.org>
diff --git a/cellular_capability_gsm.cc b/cellular_capability_gsm.cc
index 1ef2d43..cf4e551 100644
--- a/cellular_capability_gsm.cc
+++ b/cellular_capability_gsm.cc
@@ -61,6 +61,7 @@
                                 NULL);
   store->RegisterConstStringmaps(flimflam::kCellularApnListProperty,
                                  &apn_list_);
+  scanning_supported_ = true;
 }
 
 StrIntPair CellularCapabilityGSM::SimLockStatusToProperty(Error */*error*/) {