CP-5817: Productise removal of lvm2-environment-device.patch

Part of the change for rolling back lvm2-environment-device.patch. Removed code
that exports special environment variable to direct LVM to look for an
abbreviated device cache.

The second part of the change (actual removal of lvm patch) is under
guest-packages.

Signed-off-by: Chandrikas Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Zheng Li <zheng.li@eu.citrix.com>

Github: close #28 on xapi-project/sm