Avoid pending of containerized applications in case of aborting (#481)

Improvement for Docker run C++ applications with g3log 

* This addresses the case when a PID1 process crashes and the signal handling, goes into multiple or even infinite loops due to subsequent crashes. The PR makes sure to restore all signal handlers to the original signal handling after the first crash is detected. For

src/crashhandler_unix.cpp

@@ -62,15 +62,16 @@ namespace {
    // ALL thanks to this thread at StackOverflow. Pretty much borrowed from:
    // Ref: http://stackoverflow.com/questions/77005/how-to-generate-a-stacktrace-when-my-gcc-c-app-crashes
    void signalHandler(int signal_number, siginfo_t* /*info*/, void* /*unused_context*/) {
-
+
+      using namespace g3::internal;
+
       // Only one signal will be allowed past this point
       if (false == shouldDoExit()) {
-         while (true) {
+         while (shouldBlockForFatalHandling()) {
             std::this_thread::sleep_for(std::chrono::seconds(1));
          }
       }
 
-      using namespace g3::internal;
       {
          const auto dump = stackdump();
          std::ostringstream fatal_stream;
@@ -233,7 +234,13 @@ namespace g3 {
       // --- If LOG(FATAL) or CHECK(false) the signal_number will be SIGABRT
       void exitWithDefaultSignalHandler(const LEVELS& level, g3::SignalType fatal_signal_id) {
          const int signal_number = static_cast<int>(fatal_signal_id);
-         restoreSignalHandler(signal_number);
+
+         // Restore all saved signal handlers. If handling a signal which causes exiting 
+         // than let the original signal handlers to handle other signals.
+         for (const auto& sig : gSignals) {
+            restoreSignalHandler(sig.first);
+         }
+
          std::cerr << "\n\n" << __FUNCTION__ << ":" << __LINE__ << ". Exiting due to " << level.text << ", " << signal_number << "   \n\n" << std::flush;