fix: add resiliency when an integration cannot be added to a policy

[mdelapenya]

What does this PR do?

It does two things:

1. changes log.Fatal to log.Error on failures when adding an integration to a policy
2. adds a retry with maxTimeout option to the addIntegrationToPolicy method, so that we are covered on errors in the staging environment of the package-registry

[2021-12-16T05:41:55.069Z] FATA[2021-12-16T05:41:53Z] Unable to add integration to policy err="could not add package to policy; API status code = 500; response body = {"statusCode":500,"error":"Internal Server Error","message":"'502 Bad Gateway' error response from package registry at https://epr-staging.elastic.co/package/endpoint/1.4.0\"}" packageDS="{ endpoint-50fff084-9495-4633-b1a7-0a817b61d6bc Endpoint Security default cdd3d370-5e32-11ec-9ece-534be1f506d0 true [] { endpoint Endpoint Security 1.4.0}}"

Why is it important?

Resiliency in the pipeline execution

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have run the Unit tests (make unit-test), and they are passing locally
• I have run the End-2-End tests for the suite I'm working on, and they are passing locally
• I have noticed new Go dependencies (run make notice in the proper directory)

[elasticmachine]

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• Start Time: 2021-12-16T09:43:49.289+0000

• Duration: 33 min 22 sec

• Commit: b71e5ad

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Test	Results
Failed	0
Passed	86
Skipped	0
Total	86

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