The type of transport OTV control plane can use to
exchange Adjacency Server information.
'multicastAndUnicast' - OTV control plane can use both multicast
and unicast to exchange Adjacency Server
information
'unicastOnly' - OTV control plane can use only unicast
to exchange Adjacency Server information.
Value of this object can be set to 'unicastOnly' only if
the value of cotvOverlayPrimaryAdjServerAddrType is 'unknown'.