Fix timeout on NetworkAgentTest callback

All callbacks in the class use the DEFAULT_TIMEOUT_MS, except for this recently
added test.

The test is currently flaky in various branches.
Fixes: 174716714
Fixes: 174691729
Change-Id: I9f4446bb83eb4402c912292ac31d46e1d2cb6a52
Test: TH

tests/cts/net/src/android/net/cts/NetworkAgentTest.kt

@@ -570,7 +570,7 @@ class NetworkAgentTest {
                 .removeCapability(NET_CAPABILITY_NOT_VPN)
                 .removeCapability(NET_CAPABILITY_TRUSTED) // TODO: add to VPN!
                 .build()
-        val callback = TestableNetworkCallback()
+        val callback = TestableNetworkCallback(timeoutMs = DEFAULT_TIMEOUT_MS)
         registerNetworkCallback(request, callback)
 
         val nc = NetworkCapabilities().apply {