* Unit test for BF abort after after_command_before_result()

* Revised logic for handling BF abort around after command operations
* Added lighweight thread class for runtime thread id checking

include/wsrep/thread.hpp

@@ -0,0 +1,36 @@
+//
+// Copyright (C) 2018 Codership Oy <info@codership.com>
+//
+
+#include <pthread.h>
+
+namespace wsrep
+{
+    class thread
+    {
+    public:
+        class id
+        {
+        public:
+            id() : thread_() { }
+            explicit id(pthread_t thread) : thread_(thread) { }
+        private:
+            friend bool operator==(thread::id left, thread::id right)
+            {
+                return (pthread_equal(left.thread_, right.thread_));
+            }
+            pthread_t thread_;
+        };
+
+        thread()
+            : id_(pthread_self())
+        { }
+    private:
+        id id_;
+    };
+
+    namespace this_thread
+    {
+        static inline thread::id get_id() { return thread::id(pthread_self()); }
+    }
+};