Add check for empty fields in azure integration

[narph]

What does this PR do?

Adds check for empty fields in azure integration

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Build Cause: Pull request #741 updated

• Start Time: 2021-03-02T09:58:43.516+0000

• Duration: 13 min 30 sec

• Commit: 004d14f

Test stats 🧪

Test	Results
Failed	0
Passed	39
Skipped	0
Total	39

Trends 🧪

[mtojek]

The build is failing due to this: elastic/beats#24198 . If it's not an urgent issue I would wait for the correct Docker images.

Apart from this, LGTM

BTW we have introduced a Terraform service deployer that should also support Azure (if only our CI does/has secrets). You can schedule some time in the future to research this area and create a couple of tests.

[mtojek]

I think you can rebase it against master now.