Fix error in drift tests

[adolfo-ab]

Needed to cast str for ports used in ServingRuntime, otherwise fixture fails with UnprocessableEntity error

How Has This Been Tested?

Running tests in working cluster

Merge criteria:

• The commits are squashed in a cohesive manner and have meaningful messages.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work

[adolfo-ab]

/verified

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