Fixed logging for oslo versioned objects

Fixed logging for oslo versioned objects

Earlier, when we wanted to log a message with an object as a parameter,
obj_attr_is_set method used to check name parameter, which was a wrong
approach. The reason was, that the oslo logger, when received a
versioned object as a resource parameter, is trying to get the 'name'
parameter, which is a property, so the obj_attr_is_set method will
return False and the logger will try to get the 'type' parameter, which
does not exist in some versioned objects (please take a look at
oslo.logging code [1]).

Now, when the parameter's name is present in obj_extra_fields
dict, we avoid calling obj_attr_is_set and simply get() it.

The other cause was a difference between fields names: size (in volume
object) and volume_size (in snapshot object), and inproper condition
statement in lvm driver.

[1] goo.gl/YffLcK

Change-Id: Id92d58b4ccced907cc6e3e59d9e71650a459b4a8
Closes-Bug: 1501521