frag6 test cases: check more counters, wait for expiry
When done with tests check that both the per-VNET and the global-fragmented-
packets-in-system counters are zero to make sure we do not leak counters or
This implies that for all test cases we either have to check for the ICMPv6
packet sent in case of TLL=0 expiry (if it is sent) or sleep at least long
enough for the TTL to expire for all packets (e.g., fragments where we do not
have the off=0 packet).
This also means that statistics are now updated to include all the expired
There are cases when we do not check for counters to be zero and this is
when testing VNET teardown to behave properly and not panic, when we are
intentionally leaving fragments in the system.
MFC after: 3 weeks
Sponsored by: Netflix