Remove the default size in volumes_client

The config value of volume size was passed to an instance of volumes_client
and it was used as the default value if not specifying a volume size from
tests side. However, the behavior made actual tests behaviors unreadable
when checking tests code.
In addition, this behavior is different from the other service clients.
So this patch removes the default size and makes tests specify the size
clearly.

Partially implements blueprint consistent-service-method-names

Change-Id: I2a0f5841fe82ab003562749a63bc4894225699c5
18 files changed