Dell SC driver honoring folder name after volume creation.

Dell SC driver honoring folder name after volume creation.

The Dell SC driver was not honoring the volume folder name
after creation.  This has been changed so that find_volume
now checks the dell_sc_volume_folder for the requested volume
before doing a general search of the storage center.  In
either case if more than one volume is returned (two in
the dell_sc_volume_folder or two outside of that folder) then
an exception is thrown.

Also the dell_sc_volume_folder, dell_sc_server_folder and
dell_sc_ssn variables are no longer being passed arond.  They
are saved as part of the backend API object.

Tests have been updated.

Change-Id: I962ea3ed262d21deff65cdc8476939aab6ba07e2
Closes-Bug: #1449290