Modify updateConditions to use linearizable Get

[cmallikarjunah]

Ref Issue: #357

NOTE:
Added a separate function IsClusterAvailable() instead of modifying ClusterHealth(). ClusterHealth uses Serializable Get and is needed to check health against each member by other methods.
IsClusterAvailable issues a linearizable Get against each provided endpoint in turn and returns true as soon as any one responds successfully.

[kubernetes-prow]

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[kubernetes-prow]

Hi @cmallikarjunah. Thanks for your PR.

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