[CS] Remove timeout event after first available

Guarantees that timeouts are only delivered if a network never
becomes available. Once a network is available the timeout is
canceled.

Bug: 31402633
Test: all timeout related unit tests pass (new one added)
Change-Id: I2b7adffd82173cf8b99084cbfe5399961d51e148
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index de70026..5eceb9f 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -5342,6 +5342,7 @@
     // notify only this one new request of the current state
     protected void notifyNetworkCallback(NetworkAgentInfo nai, NetworkRequestInfo nri) {
         int notifyType = ConnectivityManager.CALLBACK_AVAILABLE;
+        mHandler.removeMessages(EVENT_TIMEOUT_NETWORK_REQUEST, nri);
         if (nri.mPendingIntent == null) {
             callCallbackForRequest(nri, nai, notifyType, 0);
         } else {