shill: Broadcast changes of CellularService's ActivationState property.

BUG=chromium-os:25011
TEST=tested on device

Change-Id: Iaf5e38dc7402312ac056c9a39718085c3f236ed4
Reviewed-on: https://gerrit.chromium.org/gerrit/14056
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Eric Shienbrood <ers@chromium.org>
Commit-Ready: Darin Petkov <petkov@chromium.org>
diff --git a/cellular_capability_gsm.cc b/cellular_capability_gsm.cc
index 99ef442..d5e25f5 100644
--- a/cellular_capability_gsm.cc
+++ b/cellular_capability_gsm.cc
@@ -98,7 +98,7 @@
 }
 
 void CellularCapabilityGSM::OnServiceCreated() {
-  cellular()->service()->set_activation_state(
+  cellular()->service()->SetActivationState(
       flimflam::kActivationStateActivated);
   UpdateServingOperator();
 }