thread: add blocking join

Adds a way to wait until the thread finishes its work before joining.

Change-Id: I7080a4515ce6c1158c74c6eb8973a13a4b097419

src/threadloop.cpp

@@ -110,7 +110,15 @@ ThreadLoop::join()
         thread_.join();
 }
 
-void ThreadLoop::exit()
+void
+ThreadLoop::waitForCompletion()
+{
+    if (thread_.joinable())
+        thread_.join();
+}
+
+void
+ThreadLoop::exit()
 {
     stop();
     throw ThreadLoopException();

src/threadloop.h

@@ -55,6 +55,7 @@ public:
     void exit();
     virtual void stop();
     void join();
+    void waitForCompletion(); // thread will stop itself
 
     bool isRunning() const noexcept;
     bool isStopping() const noexcept;