Prevent NullPointerException when getting OS name (#2)

* Prevent NullPointerException when getting OS name

In some environments (ie: with OpenShift), username retrieved by the system is `null`. If this is the case, it should return "unknown" (same as with unknown OS name).

Author: hdurix

src/main/java/com/github/couchmove/utils/Utils.java

@@ -45,7 +45,10 @@ private static String initializeUserName() {
                 Class<?> c = Class.forName(className);
                 Method method = c.getDeclaredMethod(methodName);
                 Object o = c.newInstance();
-                return method.invoke(o).toString();
+                Object name = method.invoke(o);
+                if (name != null) {
+                    return name.toString();
+                }
             } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException | InstantiationException | InvocationTargetException e) {
                 logger.error("Unable to get actual user name", e);
             }