Reduce Sysmtem Tray Retry Attempts

It is not essential that the system tray exists in order that the
application contuinue to function.  Reduce the number of retry
attempts which will reduce the time the application appears stalled
at startup.

This is part of the work on making the app work without the need of
system tray support as described uner #155.

src/gui/src/main.cpp

@@ -16,7 +16,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#define TRAY_RETRY_COUNT 10
+#define TRAY_RETRY_COUNT 5
 #define TRAY_RETRY_WAIT 2000
 
 #include "QBarrierApplication.h"