releng/prepare_release_branch.py: Fixups
releng/prepare_release_branch.py: Fixups

- Parameterize min and max allowed config count
- Add some print() statements for each function
- Actually delete the oldest branch config before rotation
- Block rotation if the incorrect config count is found

Signed-off-by: Stephen Augustus <f96984fef9637085f0559f1484dfd4e99545cd6e@vmware.com>

michelle192837/test-infra,michelle192837/test-infra,cjwagner/test-infra,cjwagner/test-infra,fejta/test-infra,monopole/test-infra,pwittrock/test-infra,jessfraz/test-infra,pwittrock/test-infra,brahmaroutu/test-infra,kubernetes/test-infra,jessfraz/test-infra,brahmaroutu/test-infra,cblecker/test-infra,fejta/test-infra,jessfraz/test-infra,BenTheElder/test-infra,brahmaroutu/test-infra,monopole/test-infra,fejta/test-infra,fejta/test-infra,fejta/test-infra,dims/test-infra,dims/test-infra,BenTheElder/test-infra,cblecker/test-infra,fejta/test-infra,brahmaroutu/test-infra,kubernetes/test-infra,monopole/test-infra,brahmaroutu/test-infra,pwittrock/test-infra,michelle192837/test-infra,BenTheElder/test-infra,pwittrock/test-infra,dims/test-infra,cjwagner/test-infra,cjwagner/test-infra,michelle192837/test-infra,cblecker/test-infra,BenTheElder/test-infra,dims/test-infra,BenTheElder/test-infra,cjwagner/test-infra,monopole/test-infra,kubernetes/test-infra,kubernetes/test-infra,cblecker/test-infra,kubernetes/test-infra,dims/test-infra,jessfraz/test-infra,brahmaroutu/test-infra,jessfraz/test-infra,dims/test-infra,BenTheElder/test-infra,monopole/test-infra,monopole/test-infra,cjwagner/test-infra,michelle192837/test-infra,michelle192837/test-infra,cblecker/test-infra,kubernetes/test-infra,cblecker/test-infra,pwittrock/test-infra,jessfraz/test-infra