Suppress rpc trace stack from API/CLI error
Suppress rpc trace stack from API/CLI error

Example current behavior:
$ openstack congress datasource create --config username=admin --config tenant_name=admin  --config auth_url=http://127.0.0.1:5000/v3 --config password=password --config poll_time=5 nova nova
Datasource already in use with name nova
Traceback (most recent call last):

  File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/server.py", line 153, in _process_incoming
    res = self.dispatcher.dispatch(message)

  File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 213, in dispatch
    return self._do_dispatch(endpoint, method, ctxt, args)

  File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 183, in _do_dispatch
    result = func(ctxt, **new_args)

  File "/opt/stack/congress/congress/dse2/datasource_manager.py", line 131, in add_datasource
    return self.ds_manager.add_datasource(items)

  File "/opt/stack/congress/congress/dse2/datasource_manager.py", line 71, in add_datasource
    raise exception.DatasourceNameInUse(value=req['name'])

DatasourceNameInUse: Datasource already in use with name nova
 (HTTP 409) (Request-ID: req-3dffcf58-375a-4a01-b1f9-f602a3951e2b)

Example new behavior
$ openstack congress datasource create --config username=admin --config tenant_name=admin  --config auth_url=http://127.0.0.1:5000/v3 --config password=password --config poll_time=5 nova nova
Datasource already in use with name nova (HTTP 409) (Request-ID: req-ff949f7b-c458-43cb-9ed8-698f14047fce)

Closes-Bug: 1707329

Change-Id: Ib1f5d2772dfef488d7333402dd97bcda7a8714c4

openstack/congress,openstack/congress