Remove NetworksIPV6TestAttrs duplicate tests

NetworksIpV6TestAttrs should be just for ipv6_subnet_attributes of
Neutron the class runs the other basic tests which are the same as
NetworksIpV6Test. NetworksIpV6TestAttrs doesn't need to run these
tests at all, that is just spending operating time.

Change-Id: Ic8de688fd080c0dc7f3ebf97b96b4a458becc91d
Closes-Bug: #1620734
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added blank lines for pep8
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1 file changed