Don't perform retry_execute in certain cases.

Certain cases like "LVM not found" and "Insufficient space"
in LVM create/delete shouldn't be retried.

Change-Id: I1a0891f769d37dc858c70b07c838f9fc4111a76c
Modify check for volume-type-id to a get w/default

While implementing Fix for a previous bug to enable setting
volume type on a cloned volume and reading it's info we added
a vref['volume_type_id'], problem is that the _do_clone method
is shared for both clone and create from snapshot.

In the create from snapshot case however that key doesn't exist
in the vref (which is a snapshot object).

This change turns this into a key.get with a default return.

Fixes bug: 1192745

Change-Id: I1a6d38de614f54fcaa31ea7cc4250aacc85b0796
fix error class path in logging sample

class path for NullHandler should be
cinder.openstack.common.log.NullHandler.

Fixes bug: 1192765
Change-Id: I552fe25cb89fa911dcbacb733013097b6e3c4ef3
Merge "Don't perform retry_execute in certain cases."
Merge "Modify check for volume-type-id to a get w/default"