Fix flaky test

FAIL: //cmd/kas/kasapp:kasapp_test (see /private/var/tmp/_bazel_olga/5cd39ee57871e2433de98da73525259b/execroot/gitlab_k8s_agent/bazel-out/darwin_arm64-fastbuild-ST-61abbe76aa1f/testlogs/cmd/kas/kasapp/kasapp_test/test.log)
INFO: From Testing //cmd/kas/kasapp:kasapp_test:
==================== Test output for //cmd/kas/kasapp:kasapp_test:
--- FAIL: TestTunnelFinder_PollStartsSingleGoroutineForUrl (0.21s)
    logger.go:130: 2022-05-03T02:25:00.638Z     DEBUG   Trying tunnel   {"kas_url": "grpc://pipe"}
    logger.go:130: 2022-05-03T02:25:00.839Z     DEBUG   Trying tunnel   {"kas_url": "grpc://pipe"}
    router_kas_tunnel_finder.go:104: Unexpected call to *kasapp.MockKasPool.Dial([context.Background.WithCancel.WithCancel grpc://pipe]) at cmd/kas/kasapp/router_kas_tunnel_finder.go:104 because: 
        expected call at cmd/kas/kasapp/router_kas_tunnel_finder_test.go:78 has already been called the max number of times
FAIL