Add an ability to create full clone instead of snapshot

[kayrus]

Resolves #78

[kayrus]

I think it makes sense to rename the clone: "true" to method: clone. The reason behind this:

• cinder supports volume backups and upload volume to glance image methods
• manila will support share backup feature at some point: https://blueprints.launchpad.net/manila/+spec/share-backup

[kayrus]

I think I'll split this PR into a couple: metadata, configurable timeouts and new snapshot methods

[kayrus]

@Lirt ready for review

[Lirt]

Hi @kayrus, the code looks great as usual.

I spent a while comparing the Manila snapshot and clone method. As far as I understand Manila doesn't have clone operation supported in backend and the difference there is that clone method will create snapshot and immediately create share from it and then remove snapshot while snapshot method will keep only snapshot of the share. Is it correct?

I added one comment regarding review, but it's (again) only about log message.

[kayrus]

Is it correct?

correct.

[Lirt]

Ready for merge?

[kayrus]

@Lirt yes