LISP: Modernize packet parsing

LISP: Modernize packet parsing

Define ND_LONGJMP_FROM_TCHECK and remove a 'trunc' label.
Make a bounds check conditional.
Use ND_ICHECK_U() for a length test.
Fix a bounds check, not invalid, but truncated.
(The bounds check is done by hex_print_with_offset() via hex_print().)
Use ND_TTEST_LEN() instead of testing ndo->ndo_snapend.
Remove an useless variable ('packet_iterator' same as 'bp').

Remove/update some comments.
Fix some indentations.
Remove some extra blank lines.

Update the outputs of two tests accordingly.