[py] Add API client bindings for the trial license.
[py] Add API client bindings for the trial license.

The methods begin_trial and end_trial use the endpoints /cm/trial/begin and
/cm/trial/end respectively to begin and end the trial license.

cdapio/cm_api,cdapio/cm_api,cdapio/cm_api,cloudera/cm_api,cloudera/cm_api,cdapio/cm_api,cloudera/cm_api