DevReattacher: Spinlock-protect stop() call

Replace the current delay timeout mechanism with a spinlock.
Both mechanisms try to eliminate the possibility of an in-flight
async op accessing state that has been destroyed by stop().

But the spinlock is less arbitrary.

smocore/include/deviceManager/deviceReattacher.h

@@ -5,6 +5,7 @@
 #include <atomic>
 #include <memory>
 #include <boost/asio/deadline_timer.hpp>
+#include <spinLock.h>
 
 namespace smo {
 
@@ -35,7 +36,8 @@ private:
 
     DeviceManager &parent;
     std::shared_ptr<ComponentThread> ioThread;
-    std::atomic<bool> shouldContinue;
+    SpinLock shouldContinueLock;
+    bool shouldContinue;
     boost::asio::deadline_timer timer;
 };