Add test to verify callbacks for enable/disableInterface APIs

For some reason, InterfaceStateListener callbacks when calling
enableInterface() / disableInterface() were missing test coverage.

Test: atest EthernetManagerTest
Change-Id: I7ad553746d3839097c2878934d79219efde267c8
diff --git a/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt b/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
index b7e5205..7af3c83 100644
--- a/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
+++ b/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
@@ -899,6 +899,20 @@
     }
 
     @Test
+    fun testEnableDisableInterface_callbacks() {
+        val iface = createInterface()
+        val listener = EthernetStateListener()
+        addInterfaceStateListener(listener)
+        listener.expectCallback(iface, STATE_LINK_UP, ROLE_CLIENT)
+
+        disableInterface(iface).expectResult(iface.name)
+        listener.expectCallback(iface, STATE_LINK_DOWN, ROLE_CLIENT)
+
+        enableInterface(iface).expectResult(iface.name)
+        listener.expectCallback(iface, STATE_LINK_UP, ROLE_CLIENT)
+    }
+
+    @Test
     fun testUpdateConfiguration_forBothIpConfigAndCapabilities() {
         val iface = createInterface()
         val cb = requestNetwork(ETH_REQUEST.copyWithEthernetSpecifier(iface.name))