DO NOT MERGE: revert change preventing NULL SSID in a WifiConfiguration

bug: 15114340

Change-Id: Ic66363fc7781a1d65e5b8647843a752c048145a1
(cherry picked from commit 7aa05179b970e9f1346374f1e506a2cfeaff060a)

wifi/java/android/net/wifi/WifiConfiguration.java

@@ -509,8 +509,6 @@ public class WifiConfiguration implements Parcelable {
      * @hide
      */
     public boolean isValid() {
-        if (SSID == null)
-            return false;
 
         if (allowedKeyManagement == null)
             return false;