fix: reset to default settings if healthCheck is removed (#369)

[scottlaiaws]

What type of PR is this?
bug

Which issue does this PR fix:
#369

What does this PR do / Why do we need it:
Fix bug #369 by resetting the health check configuration to default setting if healthCheck section is removed

If an issue # is not available please add repro steps and logs from aws-gateway-controller showing the issue:

Testing done on this change:
Manual testing, confirmed health check configuration is reset if removed. Also ran e2e tests

Ran 31 of 31 Specs in 2030.679 seconds
SUCCESS! -- 31 Passed | 0 Failed | 0 Pending | 0 Skipped
--- PASS: TestIntegration (2031.56s)
PASS
ok      github.com/aws/aws-application-networking-k8s/test/suites/integration   2031.595s

Automation added to e2e:
N/A

Will this PR introduce any new dependencies?: No

Will this break upgrades or downgrades. Has updating a running cluster been tested?:

Does this PR introduce any user-facing change?: Yes

fix bug #369 

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[scottlaiaws]

Previous PR: #400

[coveralls]

Pull Request Test Coverage Report for Build 6251576134

• 71 of 71 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.4%) to 39.06%

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Totals
Change from base Build 6251256284:	0.4%
Covered Lines:	4031
Relevant Lines:	10320

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💛 - Coveralls

[zijun726911]

LGTM, Seems previous PR accidentally closed