Test Disable IPv6

https://github.com/longhorn/longhorn/issues/2136

https://github.com/longhorn/longhorn/issues/2197

Longhorn v1.1.1 should work with IPv6 disabled.

Scenario

  1. Install Kubernetes
  2. Disable IPv6 on all the worker nodes using the following 
    Go to the folder /etc/default
In the grub file, edit the value GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1"
Once the file is saved update by the command update-grub
Reboot the node and once the node becomes active, 
Use the command cat /proc/cmdline to verify "ipv6.disable=1" is reflected in the values
  3. Deploy Longhorn and test basic use cases.
    1. Accessing the UI for CRUD RWO/RWX volumes
    2. Use kubectl to create workloads using RWO/RWX volumes.
  4. Re-enable ipv6 on all the nodes using: 
    By deleting the "ipv6.disable=1" from the GRUB_CMDLINE_LINUX_DEFAULT accessing grub file from /etc/default
Perform a reboot and once the node comes active
Use the command cat /proc/cmdline to verify "ipv6.disable=1" is not reflected in the values
  5. Make sure the basic use cases still works.
[Edit]