samples/bpf: extend test_tunnel_bpf.sh with ip6gre

Extend existing tests for vxlan, gre, geneve, ipip, erspan,
to include ip6 gre and gretap tunnel.

Signed-off-by: William Tu <u9012063@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>