KNOX-3033 Add option to set the correct path for sticky session cookies

[stoty]

… instead of appending the role name

What changes were proposed in this pull request?

Add a new dispatch property to generate the sticky session cookie path from the service routes, and use a default or configured sticky session cookie name without appending the service role to it.

This is expected to be necessary for integration with external load balancers like the AWS Application load balancer which expect a single sticky cookie name.

How was this patch tested?

Deployed the changes on a live cluster, set the new parameter and checked the cookie name and path set by Knox. Also added some unit tests.