Changing directory structure for Cinder clients

The tempest/services/volume directory had the following structure:

        tempest
        |___services
            |___volume
                |____json
                |    |____admin
                |    |    |____<client files>
                |    |
                |    |____<client files>
                |
                |____v2
                     |____json
                          |____admin
                          |    |____<client files>
                          |
                          |____<client files>

The structure was changed to keep consistency with other clients directories.
For example, the tempest/services/identity derectory and the tempest/services/image
directory. So now the structure is the following:

        tempest
        |___services
            |___volume
                |____base
                |    |____<client files>
                |
                |____v1
                |    |____json
                |         |____admin
                |         |    |____<client files>
                |         |
                |         |____<client files>
                |
                |____v2
                     |____json
                          |____admin
                          |    |____<client files>
                          |
                          |____<client files>

The tempest/services/volume/base directory was created and now it containes base
client files with base client classes for v1 and v2 Cinder clients.

Change-Id: I0ac37e15eddffb12d150dcd5b68e0f933712d22c
diff --git a/tempest/clients.py b/tempest/clients.py
index b685bb7..2566d79 100644
--- a/tempest/clients.py
+++ b/tempest/clients.py
@@ -119,22 +119,22 @@
 from tempest.services.telemetry.json.alarming_client import AlarmingClient
 from tempest.services.telemetry.json.telemetry_client import \
     TelemetryClient
-from tempest.services.volume.json.admin.volume_hosts_client import \
+from tempest.services.volume.v1.json.admin.volume_hosts_client import \
     VolumeHostsClient
-from tempest.services.volume.json.admin.volume_quotas_client import \
+from tempest.services.volume.v1.json.admin.volume_quotas_client import \
     VolumeQuotasClient
-from tempest.services.volume.json.admin.volume_services_client import \
+from tempest.services.volume.v1.json.admin.volume_services_client import \
     VolumesServicesClient
-from tempest.services.volume.json.admin.volume_types_client import \
+from tempest.services.volume.v1.json.admin.volume_types_client import \
     VolumeTypesClient
-from tempest.services.volume.json.availability_zone_client import \
+from tempest.services.volume.v1.json.availability_zone_client import \
     VolumeAvailabilityZoneClient
-from tempest.services.volume.json.backups_client import BackupsClient
-from tempest.services.volume.json.extensions_client import \
+from tempest.services.volume.v1.json.backups_client import BackupsClient
+from tempest.services.volume.v1.json.extensions_client import \
     ExtensionsClient as VolumeExtensionClient
-from tempest.services.volume.json.qos_client import QosSpecsClient
-from tempest.services.volume.json.snapshots_client import SnapshotsClient
-from tempest.services.volume.json.volumes_client import VolumesClient
+from tempest.services.volume.v1.json.qos_client import QosSpecsClient
+from tempest.services.volume.v1.json.snapshots_client import SnapshotsClient
+from tempest.services.volume.v1.json.volumes_client import VolumesClient
 from tempest.services.volume.v2.json.admin.volume_hosts_client import \
     VolumeHostsV2Client
 from tempest.services.volume.v2.json.admin.volume_quotas_client import \