[BUG][opensearch] setting vm.max_map_count=262144 on GKE fails

[bluehawk27]

Describe the bug
setting vm.max_map_count=262144 on gke with the security context via the helm chart currently does not work.

To Reproduce
Steps to reproduce the behavior:

1. set sysctlVmMaxMapCount: 262144
2. set sysctl.enabled: true
3. Apply helm chart
4. sysctl error on GKE

Expected behavior
Sysctl should set the vm.max_map_count

Chart Name
opensearch

Screenshots
If applicable, add screenshots to help explain your problem.

Host/Environment (please complete the following information):

• Helm Version: [e.g. 3.5.4]
• Kubernetes Version: [e.g. 1.19.x]

Do you have any additional context?
Current workaround is to run an init container to achieve the same goal:

`extraInitContainers:

name: ini-sysctl
securityContext:
runAsUser: 0
privileged: true
image: busybox:latest
command: ['sysctl', '-w','vm.max_map_count=262144']`

[DandyDeveloper]

@bluehawk27 I am going to close this as a duplicate of #87

Theres a slow discussion surrounding this there.

For GKE, it seems marking the initContainer as a privileged: true is the only workaround for this.