Update lightstreamer image (#2117)

* Update Lightstreamer version number

library/lightstreamer

@@ -1,6 +1,6 @@
 # maintainer: Lightstreamer Server Development Team <[email protected]> (@lightstreamer)
 
-6.0.2: git://github.com/Lightstreamer/Docker@ac09cec81d3dacc9175371815e42a2b7495473b4 6.0
-6.0: git://github.com/Lightstreamer/Docker@ac09cec81d3dacc9175371815e42a2b7495473b4 6.0
-6: git://github.com/Lightstreamer/Docker@ac09cec81d3dacc9175371815e42a2b7495473b4 6.0
-latest: git://github.com/Lightstreamer/Docker@ac09cec81d3dacc9175371815e42a2b7495473b4 6.0
+6.0.3: git://github.com/Lightstreamer/Docker@784b417d4415e12f1bb1b15f7f697273de3a7ded 6.0
+6.0: git://github.com/Lightstreamer/Docker@784b417d4415e12f1bb1b15f7f697273de3a7ded 6.0
+6: git://github.com/Lightstreamer/Docker@784b417d4415e12f1bb1b15f7f697273de3a7ded 6.0
+latest: git://github.com/Lightstreamer/Docker@784b417d4415e12f1bb1b15f7f697273de3a7ded 6.0