Add Restart task to CassandraTasks

[burmanm]

What this PR does: Creates a new option that does rolling restart outside cads-operator's controller.

Which issue(s) this PR fixes: Fixes #385

Checklist

• [x] Changes manually tested
• [x] Automated Tests added/updated
• [ ] Documentation added/updated
• [x] CHANGELOG.md updated (not required for documentation PRs)
• [x] CLA Signed: DataStax CLA