[AGENT-12890] Handle un-initialized expiration for oauth token

[dkirov-dd]

What does this PR do?

Adds a condition where the read function can handle the case self._expiration is None

Motivation

The self._expiration attribute is not initialized, so the get_timestamp() >= self._expiration would fail as it compares int to None.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.47%. Comparing base (511fef8) to head (a95d13e).

Additional details and impacted files

Flag	Coverage Δ
activemq	?
cassandra	?
hive	?
hivemq	?
hudi	?
ignite	?
jboss_wildfly	?
kafka	?
presto	?
solr	?

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