VDR-connected networks were using designated DHCP Edge appliances
to provide metadata.
That was necessary before we introduced option 121 - which can be
used for route injection, which directs metadata traffic towards the
DHCP Edge.
This change removes some redundant code which is supporting metadata
in the old manner.
The patch deprecates supports of older versions of NSX which do not
support insertion of host routes which is required for the change.
Therefore dhcp_force_metadata config parameter has been deprecated.
Change-Id: I6b5e2acf09ce61c87d8ae97471955599cddf320b
df8f34c66d