Handle all the exception types defined by senlin

Currently some exceptions defined by senlin are not or not correctly mapped to standard http exception, which will cause a internal error. These exceptions should be properly handled.
* Fix the exception types which are wrongly mapped to standard http exception(not internal error).
* Check the exception types created by senlin which are not mapping to standard http exception(not internal error), and correctly map them.
* Check the use of HTTPInternalServerError.

* Handling the exception from openstackSDK

** First, implement a parse_exception method to parse the exception type from openstackSDK. (Refer to http://git.openstack.org/cgit/stackforge/python-senlinclient/tree/senlinclient/common/exc.py#n228)
** Then catch the SDK exceptions wherever they happen, and use parse_exception to parse them.
The code is like:
  try:
      self.conn.do_something()
  except Exception as ex:
      raise exutil.parse_exception(ex) # parse_exception method should return an InternalError.
** In the upper layer, catch the InternalError and translate it to the proper senlin exception type by checking the error code and error message.
  try:
     nova_driver.flavor_get(flavor_id)
  except InternalError as ex:
     LOG.exception(xxx)
     raise SenlinBadRequest()