Deflake pilot mc tests by sending single requests (#32750)
Deflake pilot mc tests by sending single requests (#32750)

Without explicitly setting count=1, we default to sending 15 calls with
converge=3 meaning 45 calls must succeed in a row for the test to pass.
This leads to a lot of flakes. After analyzing 10+ of these, it seems
its just due to resource contention in CI, not any bugs in Istio,
triggering this.

This drops tests that can be exercised with a single request to do so.
istio/istio,istio/istio,istio/istio,istio/istio,istio/istio