Add better IPv6 addr match check when starting node

[TrimBiggs]

Fixes #901

[robbrockbank]

It looks fine, but I can't help thinking the get_host_ips() should really return a list of IPAddress objects. Wonder if we should update it. More work though.

[TrimBiggs]

I updated to reflect your comment, see the libcalico change projectcalico/libcalico#105, which must be merged before this can be merged.

[robbrockbank]

You should grep the code for instances of get_host_ps. We also use this in the ST utils class - that'll need fixing up.

[TrimBiggs]

I've updated this to fix the use of get_host_ips in test_util.py.

[robbrockbank]

LGTM