Bump etcd to address CVE

[dpippenger]

The etcd 3.3.15 used in the current chart contains a number of CVE that could be addressed by bumping to 3.3.24.

https://nvd.nist.gov/vuln/detail/CVE-2020-15106
https://nvd.nist.gov/vuln/detail/CVE-2020-15113
https://nvd.nist.gov/vuln/detail/CVE-2020-15114
https://nvd.nist.gov/vuln/detail/CVE-2020-15115

While these may or may not have a practical impact on VVP due to environmental mitigation, pushing to a patched version will help all of us evaluating the security posture in deployed scenarios.