shill: wifi: Reconnect to reappearing WPA supplicant instances.

Currently DBusManager doesn't guarantee that appear/vanish messages
alternate. Ensure that WiFi reconnects to a new WPA supplicant
instance even in the case when there's no wpa_supplicant-vanished
message between supplicant instances. Also, some log cleanup.

BUG=chromium-os:31712
TEST=unit test, tested on device

Change-Id: I42e0ba0487c60ebc67d1eee49018093bd7f06344
Reviewed-on: https://gerrit.chromium.org/gerrit/26662
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Darin Petkov <petkov@chromium.org>
diff --git a/wifi_service.cc b/wifi_service.cc
index f32923d..68f528a 100644
--- a/wifi_service.cc
+++ b/wifi_service.cc
@@ -121,9 +121,7 @@
   IgnoreParameterForConfigure(flimflam::kWifiHiddenSsid);
 }
 
-WiFiService::~WiFiService() {
-  LOG(INFO) << __func__;
-}
+WiFiService::~WiFiService() {}
 
 bool WiFiService::IsAutoConnectable(const char **reason) const {
   if (!Service::IsAutoConnectable(reason)) {