o Minor bugfixes
    - Control port was using set_max_file_descriptors() with a limit set to
      0 to get the max value. A recent fix made this use case return an
      error and introduced dead code in that function. This triggered a
      warning that our limit (ConnLimit) was invalid but in reality it was
      not.
      
      Now, to the control port uses a specific getter function to query the
      value and set_max_file_descriptors() should never be used again for
      that purpose. Fixes #16697; bugfix on 0.2.7.2-alpha.