Fix writing of advanced settings

After reading from stream we must return again to line 0 if we
want to read file again

Author: TomasKorbar

serversettings.py

@@ -440,6 +440,9 @@ def saveAdvanced (self):
                 has_browsepoll = True
                 break
 
+        # Return to the start of file
+        f.seek(0)
+
         for line in f:
             line = line.decode('UTF-8')
             l = line.lower ().strip ()