Fix TestAccCosmicStaticNAT_basic test
Fix TestAccCosmicStaticNAT_basic test

`cosmic.PublicIpAddress` does not contain a `Associatednetworkname` field; since
we are intersted in associating the IP with a running VM, this test now looks up
the `Virtualmachinename` field for comparison.

Signed-off-by: Stephen Hoekstra <2371e4836dca2b4ff2f5fe1e3b942f4fa01b2f56@schubergphilis.com>

xanzy/terraform-provider-cosmic