Fix lint errors

[huoqifeng]

Fix the golangci-lint errors in https://github.com/zhmcclient/golang-zhmcclient/actions/runs/6333842494/job/17202544924, as below:

• Fix the lint errors
• Enable the golangci-lint action after fix all lint errors in https://github.com/zhmcclient/golang-zhmcclient/actions/workflows/golangci-lint.yml

run golangci-lint
Running [/home/runner/golangci-lint-1.54.2-linux-amd64/golangci-lint run --out-format=colored-line-number,github-actions] in [] ...
Error: pkg/zhmcclient/client.go:370:10: Error return value of c.Logon is not checked (errcheck)
c.Logon()
^
Error: pkg/zhmcclient/client.go:371:18: Error return value of c.executeUpload is not checked (errcheck)
c.executeUpload(requestType, url.String(), requestData)
^
Error: pkg/zhmcclient/client.go:403:10: Error return value of c.Logon is not checked (errcheck)
c.Logon()
^
pkg/zhmcclient/client.go:1: File is not gofmt-ed with -s (gofmt)

Error: sample.go:401:6: ineffectual assignment to processorMode (ineffassign)
var processorMode zhmcclient.PartitionProcessorMode = ""
^
Error: pkg/zhmcclient/model.go:24:2: SA9004: only the first constant in this group has an explicit type (staticcheck)
ADAPTER_FAMILY_HIPERSOCKET AdapterFamily = "hipersockets"
^
Error: pkg/zhmcclient/model.go:35:2: SA9004: only the first constant in this group has an explicit type (staticcheck)
ADAPTER_TYPE_CRYPTO AdapterType = "crypto"
^
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA9004: only the first constant in this group has an explicit type (staticcheck)
Error: SA1019: "io/ioutil" has been deprecated since Go 1.19: As of Go 1.16, the same functionality is now provided by package io or package os, and those implementations should be preferred in new code. See the specific function documentation for details. (staticcheck)

Error: issues found
Ran golangci-lint in 3663ms