Move ExecResult definition to models.containers

Signed-off-by: Joffrey F <joffrey@docker.com>

docker/models/containers.py

 import copy
+from collections import namedtuple
 
 from ..api import APIClient
 from ..errors import (ContainerError, ImageNotFound,
                       create_unexpected_kwargs_error)
-from ..types import ExecResult, HostConfig
+from ..types import HostConfig
 from ..utils import version_gte
 from .images import Image
 from .resource import Collection, Model
@@ -173,10 +174,11 @@ class Container(Model):
         )
         if socket or stream:
             return ExecResult(None, exec_output)
-        else:
-            return ExecResult(
-                self.client.api.exec_inspect(resp['Id'])['ExitCode'],
-                exec_output)
+
+        return ExecResult(
+            self.client.api.exec_inspect(resp['Id'])['ExitCode'],
+            exec_output
+        )
 
     def export(self):
         """
@@ -1007,3 +1009,8 @@ def _host_volume_from_bind(bind):
         return bits[0]
     else:
         return bits[1]
+
+
+ExecResult = namedtuple('ExecResult', 'exit_code,output')
+""" A result of Container.exec_run with the properties ``exit_code`` and
+    ``output``. """

docker/types/__init__.py

 # flake8: noqa
-from .containers import (ContainerConfig, ExecResult, HostConfig, LogConfig,
-                         Ulimit)
+from .containers import ContainerConfig, HostConfig, LogConfig, Ulimit
 from .healthcheck import Healthcheck
 from .networks import EndpointConfig, IPAMConfig, IPAMPool, NetworkingConfig
 from .services import (

docker/types/containers.py

-from collections import namedtuple
 import six
 import warnings
 
@@ -12,11 +11,6 @@ from .base import DictType
 from .healthcheck import Healthcheck
 
 
-ExecResult = namedtuple('ExecResult', 'exit_code,output')
-""" A result of Container.exec_run with the properties ``exit_code`` and
-    ``output``. """
-
-
 class LogConfigTypesEnum(object):
     _values = (
         'json-file',