engine: Remove unused code

The removed method and constant are being used.

Change-Id: Ic926cf9f2944bef43fc9e80d23ba80154b9f185b
Signed-off-by: Moti Asayag <masayag@redhat.com>
engine: Consider case-sensitivity for mac-address uniqueness

The patch modifies the type of the map which holds the
MAC Address to be case-insensitive to prevent adding
the same MAC address with a different capitalization.

Change-Id: I57516cc710648b37a9cebcdfce592c2418a7e192
Bug-Url: https://bugzilla.redhat.com/973911
Signed-off-by: Moti Asayag <masayag@redhat.com>