Fix staticheck warnings, update dependencies

Makefile

go.mod

go.sum

main.go

vendor/github.com/gophercloud/gophercloud/.travis.yml

vendor/github.com/gophercloud/gophercloud/CHANGELOG.md

vendor/github.com/gophercloud/gophercloud/README.md

vendor/github.com/gophercloud/gophercloud/doc.go

vendor/github.com/gophercloud/gophercloud/go.mod

vendor/github.com/gophercloud/gophercloud/go.sum

...loud/gophercloud/openstack/compute/v2/servers/requests.go

...r/github.com/gophercloud/gophercloud/pagination/linked.go

vendor/github.com/gophercloud/gophercloud/provider_client.go

vendor/github.com/gophercloud/gophercloud/util.go

vendor/github.com/gophercloud/utils/client/client.go

vendor/github.com/gophercloud/utils/internal/pkg.go

vendor/github.com/gophercloud/utils/internal/util.go

....com/gophercloud/utils/openstack/clientconfig/requests.go

...b.com/gophercloud/utils/openstack/clientconfig/results.go

...hub.com/gophercloud/utils/openstack/clientconfig/utils.go