provider/statuscake: fix StatusCake tests

[ruippeixotog]

This pull request updates the vendored DreamItGetIT/statuscake package to its latest version in order to include a fix regarding contact IDs. It also fixes the CreateTest and UpdateTest functions, which were not setting all attributes supported by statuscake_test resources.

The existing bug resulted in having resource states inconsistent with the respective entities in StatusCake. As a way to prevent that in the future I extended the existing tests to include consistency checks for attributes.

This is pretty much my first time writing Go code, so I probably missed some idioms and style considerations. Suggestions for improvements are welcome :)

Fixes #8708.

[stack72]

Thanks so much for the work here @ruippeixotog

This LGTM!

% make testacc TEST=./builtin/providers/statuscake
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2016/12/11 19:41:05 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/statuscake -v  -timeout 120m
=== RUN   TestProvider
--- PASS: TestProvider (0.00s)
=== RUN   TestProvider_impl
--- PASS: TestProvider_impl (0.00s)
=== RUN   TestAccStatusCake_basic
--- PASS: TestAccStatusCake_basic (1.60s)
=== RUN   TestAccStatusCake_withUpdate
--- PASS: TestAccStatusCake_withUpdate (3.09s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/statuscake	4.704s

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