Return "post" route middleware if "get" route not available

* The everymodule just only return the "get" route middleware and
  no "post" route middleware returning. As such, if the "endpointAlias"
  of "get" route is not available, try "post" route also.
  Finally, if neither of them available just return undefined.

  This case is neccessary for the "everyauth-password" module as it
  requires the "post" route middleware to handle credentials process.