OpenShift 4 compatibility

[mhutter]

Describe the bug

When running against OCP4, I get deprecation errors and the seiso aborts due to an error.

Additional context

Target is an OCP 4.8 cluster

Logs

seiso configmap --delete --older-than 3w -l app=waf-${APP_NAME} -l component=waf -l environment=${ENVIRONMENT}
level=info msg="Seiso 0.8.0, commit dbf5fecf9e58205d529e12ed2a37bb85956cf4a1, date 2021-05-07T13:26:38Z"
W1019 16:35:33.924140      75 warnings.go:70] batch/v1beta1 CronJob is deprecated in v1.21+, unavailable in v1.25+; use batch/v1 CronJob
W1019 16:35:34.159983      75 warnings.go:70] batch/v1beta1 CronJob is deprecated in v1.21+, unavailable in v1.25+; use batch/v1 CronJob
W1019 16:35:34.326158      75 warnings.go:70] batch/v1beta1 CronJob is deprecated in v1.21+, unavailable in v1.25+; use batch/v1 CronJob
W1019 16:35:34.521664      75 warnings.go:70] batch/v1beta1 CronJob is deprecated in v1.21+, unavailable in v1.25+; use batch/v1 CronJob
W1019 16:35:34.726626      75 warnings.go:70] batch/v1beta1 CronJob is deprecated in v1.21+, unavailable in v1.25+; use batch/v1 CronJob
Error: could not retrieve unused config maps for 'tpl-masterdata-development': the server could not find the requested resource

Expected behavior

Seiso not aborting :)

To Reproduce

2. Commands

seiso configmap --delete --older-than 3w 

Environment (please complete the following information):

• Image Version: e.g. 0.8.0
• K8s Version: e.g. v1.21
• K8s Distribution: e.g. OpenShift 4