[BUG] Unable to update existing priority label to new priority label

[sanjay7178]

Describe the bug
Currently when a existing priority label is present and wanted to make update to new one , it adds another one instead of updating existing label

To Reproduce
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1. Using command '...'
2. With settings '...'
3. See error

Expected behavior
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Github repo

sanjay7178/kube-burner#3

Logs
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Additional info
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