VPP-437: ip6 hbh processing with FIB 2.0

VPP-437: ip6 hbh processing with FIB 2.0

1. Modifies ip6 hbh selective processing in lookup
only when non-recursive routes are present.
2. Adds ip6 hbh processing in load balance.
3. Cleanup of ip6 iOAM hbh plugin formatting and
CLI handling found while testing the changes.
4. Deleted wrong asserts in dual loop for add
and pop iOAM hbh nodes. The current data of the buffer
ip6 start and will not be 0
5. Deleted set ioam destination cli and associate functions.
iOAM add/pop is enabled via classifier, this cli is no longer
used.

Change-Id: I3aac71ad512762c0b2b602fe88fe0291b85d39c7
Signed-off-by: Shwetha <shwethab@cisco.com>