fix the default cookie name in doc

[rajatjindal]

What this PR does / why we need it:

Fix the documentation and example for cookie based session-affinity

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

[rajatjindal]

/assign @justinsb

[codecov-io]

Codecov Report

Merging #2372 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #2372      +/-   ##
=========================================
- Coverage   39.12%   39.1%   -0.02%     
=========================================
  Files          73      73              
  Lines        5204    5204              
=========================================
- Hits         2036    2035       -1     
- Misses       2878    2880       +2     
+ Partials      290     289       -1

Impacted Files	Coverage Δ
internal/watch/file_watcher.go	80.76% <0%> (-3.85%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c37ed7e...4237f29. Read the comment docs.

[antoineco]

/lgtm missing that superpower apparently

[k8s-ci-robot]

@antoineco: changing LGTM is restricted to assignees, and only kubernetes org members may be assigned issues.

In response to this:

/lgtm

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[aledbf]

/lgtm

[aledbf]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, rajatjindal

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [aledbf]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[aledbf]

@rajatjindal thanks!

[rajatjindal]

thanks to you guys for working on such awesome opensource tools