service implementation might dead-locked

[tsingakbar]

rmw_ecal/rmw_ecal_shared_cpp/src/internal/service.hpp

Line 118 in 53b952e

req.WaitForResponse();

Before executing req.WaitForResponse(), it's possible that this request has been TakeRequested and SendResponseed in ros executor thread, and the condition variable waiting in req.WaitForResponse() totally missing the notify and blocked forever.

To increase the possiblity of reproducing this problem, add something like std::this_thread::sleep_for(std::chrono::milliseconds(5)); before req.WaitForResponse().