GO-7567: fail-point tests skip before setting mock expectations (fixes v0.7.0 release build)

[requilence]

Summary

• The v0.7.0 release build failed in TestCacheService_StalledTransactionIsBounded and TestCacheService_StalledLeaseWritesAreBounded: CI's Mongo replica set has no test commands, so failCommand skips — but gomock expectations set before it were then reported as missing calls.
• Set the fail point (and thus the skip) before the expectations. Test-only change.

Failed run: https://github.com/anyproto/any-ns-node/actions/runs/37505001570

Test plan

• Reproduced on a local replica set without test commands: main fails exactly these two tests; this branch passes ./cache/
• Replica set with test commands: ./cache/ passes (fail-point tests run)
• Release build green after re-tag (v0.7.1)

[github-actions]

New Coverage	56.2% of statements
Patch Coverage	0.0% of changed statements (0/0)

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