For the cases, where the encapsulation string
is decided at packet switch time, the adjacency
encapsulation string specified by object cefAdjEncap
require a fixup. I.e. for the adjacencies out of IP
Tunnels, the string prepended is an IP header which has
fields which can only be setup at packet switch time.
The value of this object represent the kind of fixup
applied to the packet.
If the encapsulation string doesn't require any fixup,
then the value of this object will be of zero length.