VNX: Fix failure in SnapCopy feature

VNX: Fix failure in SnapCopy feature

Previously, user needs to enable this feature via Volume Type.
See: https://review.openstack.org/#/c/184733/

This introduces some failures for volume operations, for example:

1. Creating cloned volume or snapshot from snapcopy volume will fail.
2. Creating volume from snapshot whose source volume's volume type is
snapcopy type will fail.
3. Creating non-snapcopy volume from source volume with snapcopy type
will fail.

In order to fix above issues, Driver needs to store the base LUN info
for all volumes. When creating cloned volume or volume from snapshot
, driver extracts the base LUN info and creates snapshot mount point
according to the base LUN and then exposes as a snapcopy volume.

Example cinder command to enable snapcopy on volume:

    cinder create --source-volid <vol-id> --metadata snapcopy=True
or

    cinder create --snapshot-id <snap-id> --metadata snapcopy=True

liberty-backport-potential
DocImpact
Change-Id: I91c83ddac9bcad9c7c788d7bf82bcc4dced71751
Closes-Bug: 1514319