Scheduler: Set running state for multithreaded schedulers

Make sure a started scheduler can be stopped afterwards, by setting
the expected RUNNING state.

Part of issue #217.

core/include/gnuradio-4.0/Scheduler.hpp

@@ -310,6 +310,7 @@ class Simple : public SchedulerBase<TProfiler> {
                 this->_state = lifecycle::State::ERROR;
             }
         } else if (executionPolicy == ExecutionPolicy::multiThreaded) {
+            this->_state = lifecycle::State::RUNNING;
             this->runOnPool(this->_job_lists, [this](auto &job) { return this->workOnce(job); });
         } else {
             throw std::invalid_argument("Unknown execution Policy");
@@ -446,6 +447,7 @@ class BreadthFirst : public SchedulerBase<TProfiler> {
                 }
             }
         } else if (executionPolicy == multiThreaded) {
+            this->_state = lifecycle::State::RUNNING;
             this->runOnPool(this->_job_lists, [this](auto &job) { return this->workOnce(job); });
         } else {
             throw std::invalid_argument("Unknown execution Policy");