tests: add unit tests for pkg/injector/health_probes

[shuheiktgw]

Description:

Relates to #3432
I've added missing unit tests for pkg/injector/health_probes. Thank you for your review!

Affected area:

Functional Area
New Functionality	[ ]
Documentation	[ ]
Install	[ ]
CLI Tool	[ ]
Certificate Management	[ ]
Control Plane	[ ]
Ingress	[ ]
Egress	[ ]
Networking	[ ]
Observability	[ ]
SMI Policy	[ ]
Sidecar Injection	[ ]
Security	[ ]
Upgrade	[ ]
Tests	[X]
CI System	[ ]
Demo	[ ]
Performance	[ ]
Other	[ ]

Please answer the following questions with yes/no.

1. Does this change contain code from or inspired by another project?
   • Did you notify the maintainers and provide attribution?

No

1. Is this a breaking change?

No

[codecov-commenter]

Codecov Report

Merging #3520 (5a25e19) into main (dc597c8) will decrease coverage by 0.10%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3520      +/-   ##
==========================================
- Coverage   66.25%   66.14%   -0.11%     
==========================================
  Files         169      170       +1     
  Lines        8081     8082       +1     
==========================================
- Hits         5354     5346       -8     
- Misses       2697     2706       +9     
  Partials       30       30              

Flag	Coverage Δ
unittests	66.14% <ø> (-0.11%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/envoy/cds/response.go	83.33% <0.00%> (-6.25%)	⬇️
pkg/envoy/registry/services.go	81.81% <0.00%> (-3.04%)	⬇️
pkg/envoy/ads/stream.go	3.72% <0.00%> (-1.97%)	⬇️
pkg/envoy/proxy.go	87.32% <0.00%> (-1.91%)	⬇️
pkg/envoy/sds/response.go	88.39% <0.00%> (-1.79%)	⬇️
pkg/catalog/catalog.go	92.30% <0.00%> (-0.55%)	⬇️
pkg/endpoint/providers/kube/client.go	78.00% <0.00%> (-0.22%)	⬇️
pkg/utils/proto.go	70.00% <0.00%> (ø)
cmd/osm-controller/osm-controller.go	17.29% <0.00%> (+0.12%)	⬆️
pkg/injector/envoy_config.go	90.43% <0.00%> (+1.14%)	⬆️
... and 2 more

---

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 dc597c8...5a25e19. Read the comment docs.