[WifiTrackerLib] Reset default route booleans in BaseWifiTracker#onStart

The default route booleans must be reset to false in onStart() if there
is no default route. Otherwise these booleans may still hold
an out-of-date "true" value and the actual false->true update will not
trigger handleOnDefaultRouteChanged, causing the X in the wifi signal
icon to never disappear.

Bug: 168885802
Test: Connect to network in wifi picker, open network details and
disconnect, go back to wifi picker and connect to same network. Observe
X in wifi signal icon to disappear after validation.

Change-Id: Ifde41ec0436ae67c59f5b935b5bc4ff1cd357f57
diff --git a/libs/WifiTrackerLib/src/com/android/wifitrackerlib/BaseWifiTracker.java b/libs/WifiTrackerLib/src/com/android/wifitrackerlib/BaseWifiTracker.java
index 28b1a49..8eaef6e 100644
--- a/libs/WifiTrackerLib/src/com/android/wifitrackerlib/BaseWifiTracker.java
+++ b/libs/WifiTrackerLib/src/com/android/wifitrackerlib/BaseWifiTracker.java
@@ -273,6 +273,9 @@
         if (defaultNetworkCapabilities != null) {
             mIsWifiDefaultRoute = defaultNetworkCapabilities.hasTransport(TRANSPORT_WIFI);
             mIsCellDefaultRoute = defaultNetworkCapabilities.hasTransport(TRANSPORT_CELLULAR);
+        } else {
+            mIsWifiDefaultRoute = false;
+            mIsCellDefaultRoute = false;
         }
         if (isVerboseLoggingEnabled()) {
             Log.v(mTag, "Wifi is the default route: " + mIsWifiDefaultRoute);