set maxUnavailable to 1 in addons-manager deployment

[ggpaue]

What this PR does / why we need it

set maxUnavailable to 1 for addons-manager deployment

Which issue(s) this PR fixes

Fixes #2884

Describe testing done for PR

Manual tested the change on kind cluster:

1. setup single control plane kind cluster
2. apply addons-manager.yaml to setup addons-manager deployment
3. use a new image to update addons-manager deployment
4. Verify addons-manager deployment can be updated

Release note

package-based-lcm:  set maxUnavailable to 1 in addons-manager deployment

PR Checklist

• Squash the commits into one or a small number of logical commits
  
• Use good commit messages
• Ensure PR contains terms all contributors can understand and links all contributors can access

Additional information

Special notes for your reviewer

[vijaykatam]

Change looks good to me. Were you able to test upgrade on an addons-manager previously deployed on a single control plane node to the new version?

[ggpaue]

Change looks good to me. Were you able to test upgrade on an addons-manager previously deployed on a single control plane node to the new version?

Yes, I used a local kind cluster, single node and tested deployment upgrade. Verified that maxUnavailable 25% will fail upgrade but set it to 1 will succeed

[codecov]

Codecov Report

Merging #2962 (fceb1e4) into main (e921082) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2962      +/-   ##
==========================================
- Coverage   44.00%   43.98%   -0.02%     
==========================================
  Files         416      416              
  Lines       41852    41852              
==========================================
- Hits        18415    18410       -5     
- Misses      21715    21720       +5     
  Partials     1722     1722              

Impacted Files	Coverage Δ
addons/controllers/clusterbootstrap_controller.go	63.28% <0.00%> (-0.62%)	⬇️
pkg/v1/tkg/tkgpackageclient/package_update.go	85.00% <0.00%> (+1.42%)	⬆️

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[vijaykatam]

LGTM