I assume this is a war file? If yes, the context root inside the sun-web.xml should be honored unless you specify a different context root explicitly through admin console or admin cli.
When you used the admin console to deploy the war to cluster, did you specify a different context root in the console deploy screen?
Have you tried to use admin cli to deploy the same war to the cluster to see what context root is being used? The syntax will be:
$GF_INSTALL/bin/asadmin deploy --target [your cluster name] [your war name]
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