VIF: add VIF.get_locking_mode()
VIF: add VIF.get_locking_mode()

This parses the port-locking configuration in the VIF metadata.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

thomassa/xenopsd,djs55/xenopsd,djs55/xenopsd-previous,djs55/xenopsd,djs55/xenopsd-previous,johnelse/xenopsd,johnelse/xenopsd,cheng--zhang/xenopsd,simonjbeaumont/xenopsd,euanh/xenopsd,thomassa/xenopsd,euanh/xenopsd,johnelse/xenopsd,djs55/xenopsd-previous,koushikcgit/xenopsd,koushikcgit/xenopsd,thomassa/xenopsd,simonjbeaumont/xenopsd,djs55/xenopsd,cheng--zhang/xenopsd,cheng--zhang/xenopsd,euanh/xenopsd,koushikcgit/xenopsd,simonjbeaumont/xenopsd