Create new module: Storage_utils

Signed-off-by: John Else <john.else@citrix.com>
CA-98492: Fix for VDI.create for certain VDI types

SM was using a Record_utils function to determine the type of new VDIs
and defaulting to the "user" type, which meant that redo_log and HA
statefile VDIs would erroneously be created as "user" VDIs.

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #1014 from johnelse/ca-98492

CA-98492: Fix for VDI.create for certain VDI types