fix: reverting keepalived changes after removing dependency in 2.19.1

[bejjrajesh]

Proposed changes

This MR will revert the changes introduced in the MR(#233). We have removed the keepalived dependency on the Nginx Instance Manager.

Solution:Keepalived should be installed by customer manually when setting up the NIM HA availability.

Testing: Reverting to existing working copy only.

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[mjang]

@bejjrajesh I should have asked this question for #233

• In our docs, we refer to the keepalived service for high availability.
  • If I understand your intent correctly, with this PR (MR), users in disconnected environments will have to use the high availability doc (if they want HA)

For the record, I'm approving, as this seems to be a straight "revert" from PR #233. But we need to know if there's an impact to our docs.

cc @travisamartin