[CP-5830]: Productise removal of lvm2-master-mode.patch

Removed the --master switch from lvm commands. We now use two separate
lvm conf files for master and slave nodes. Appropriate conf file is
chosen through an environment variable.

This changeset includes the fix made for [CA-116958] in addition to the
original work done for patch removal.

Signed-off-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>

GitHub: closes #48 on xapi-project/sm