Sheepdog: Improve snapshot and clone operation

Sheepdog: Improve snapshot and clone operation

This patch changes SheepdogDriver Class methods to use
SheepdogClient Class methods for detailed Error logs.

We change the following SheepdogDriver methods.

- create_snapshot
- delete_snapshot
- create_volume_from_snapshot
- create_cloned_volume
- extend_volume

SheepdogClient Class methods are implemented to enable
fine grained Error handling.

So, the administrators are enable to do error recovery
more easily using those logs.

Change-Id: Ib126088e4100739db013b21970051af1f29790d5