test(cmd): existing tests reach real AWS endpoints #2162

TestProcessService_SavingsPlansAccountLevel, TestRunToolFromCSV* and TestCSVCap* build real AWS clients and send requests to the live endpoints (IMDS and service endpoints; they fail with credential errors and slow the package to about 8 minutes). Reproduced on base 22126ab as well as on #2160. They should use a stubbed transport (see spStubTransport in cmd/savings_plan_purchase_test.go) so unit tests never leave the machine. Found while verifying #2160.