Switch to use new base_client.BaseClient

Class 'tempest.lib.services.volume.v3.base_client.BaseClient' has moved
to 'tempest.lib.services.volume.base_client.BaseClient' in version Pike
[1] and will be removed in a future version.

[1] I645ae35daebd924c4c4523163e5419cc050bb0ed

Change-Id: I4bcc9e2c7b6fd0096dc9c8f679ef680ea0d7bbbf
1 file changed