MESSENGER-3156 Fix ServerURL preselection

bwi/ServerURLs/ServerURLHelper.swift

@@ -68,6 +68,17 @@ import Foundation
         self.loadURLs()
     }
     
+    func indexOf(_ serverUrl: String) -> Int {
+        for setting in self.serverSettings {
+            if setting.serverUrl == serverUrl {
+                if let index = self.serverSettings.firstIndex(of: setting) {
+                    return index
+                }
+            }
+        }
+        return NSNotFound
+    }
+    
     func serverUrl()  -> String? {
         if serverSettings.indices.contains(selectedIndex)  {
             return serverSettings[selectedIndex].serverUrl