make request cancel sync to avoid lifetime issues in CRT

[sbiscigl]

Issue #, if available:

#3639

Description of changes:

We previous made a change #3643 to preserve the request lifetime of a request so that cancel request can run in parallel without lifetime issues. This change used a wait_for that times out at one minute then would crash. This is under the assumption that a cancel request must run in 1 minutes and waiting longer will crash. A customer is still seeing the crash which is indicative that they are running under strain, however we should run this in sync to prevent the lifetime issue all together. Running back of the napkin tests show that sync is actually faster so making this sync seems like the right thing to do.

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• Did a review by yourself.
• Added proper tests to cover this PR. (If tests are not applicable, explain.)
• Checked if this PR is a breaking (APIs have been changed) change.
• Checked if this PR will not introduce cross-platform inconsistent behavior.
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