Fix forget button on wifi details page.

- Corrected logic for forgetting the current network in the network
details page
- After a user has forgotten a network, the button becomes disabled
(TODO final UX on this - go/remaining-wifi-picker-work tracks this)
- Added unit tests for forgetting network flow
- Fixed bug where the current tethering WifiConfiguration was associated
with the currrent network

Bug: 36458941
Test: m RunSettingsRoboTests
Change-Id: Ie3c4bae8b295908b17179e60359c8bc599519744

src/com/android/settings/wifi/details/WifiDetailPreferenceController.java

@@ -149,7 +149,6 @@ public class WifiDetailPreferenceController extends PreferenceController impleme
     @Override
     public void onResume() {
         mWifiInfo = mWifiManager.getConnectionInfo();
-        mWifiConfig = mWifiManager.getWifiApConfiguration();
 
         refreshFromWifiInfo();
         setIpText();
@@ -257,4 +256,17 @@ public class WifiDetailPreferenceController extends PreferenceController impleme
         }
         mDnsPref.setDetailText(builder.toString());
     }
+
+    /**
+     * Forgets the wifi network associated with this preference.
+     */
+    public void forgetNetwork() {
+        if (mWifiConfig.ephemeral) {
+            mWifiManager.disableEphemeralNetwork(mWifiConfig.SSID);
+        } else if (mWifiConfig.isPasspoint()) {
+            mWifiManager.removePasspointConfiguration(mWifiConfig.FQDN);
+        } else {
+            mWifiManager.forget(mWifiConfig.networkId, null /* action listener */);
+        }
+    }
 }