[nginx] Fix contains check for forwarded tag

[marc-gr]

Automated PR.

Fix contains check for forwarded tag.

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[elasticmachine]

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• Start Time: 2021-10-05T08:31:25.940+0000

• Duration: 16 min 52 sec

• Commit: 1be32f6

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Test	Results
Failed	0
Passed	40
Skipped	0
Total	40

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