shill: wimax: Call UpdateConnectable after changing |need_passphrase_|.

BUG=None
TEST=Verify that UI prompts for credentials when reconnecting to a WiMAX
network after explicitly disconnecting from the network.

Change-Id: Ida27bac7639c01f0bc6add4f86bfe4320cb4187b
Reviewed-on: https://gerrit.chromium.org/gerrit/24643
Reviewed-by: Darin Petkov <petkov@chromium.org>
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
diff --git a/wimax_service.cc b/wimax_service.cc
index a2f0fef..35b3cfd 100644
--- a/wimax_service.cc
+++ b/wimax_service.cc
@@ -169,6 +169,7 @@
   // TODO(benchan,petkov): Find a better way to allow users to change the
   // EAP credentials.
   need_passphrase_ = true;
+  UpdateConnectable();
 }
 
 string WiMaxService::GetStorageIdentifier() const {