use ‘%T’ instead of ‘%x’, to avoid log4j NDC failure. https://github.com/wu-sheng/sky-walking/issues/77

skywalking-application-toolkit/skywalking-toolkit-log4j-1.x/src/main/java/com/a/eye/skywalking/toolkit/log/log4j/v1/x/TraceIdPatternParser.java

@@ -13,7 +13,7 @@ public class TraceIdPatternParser extends PatternParser {
 
     @Override
     protected void finalizeConverter(char c) {
-        if ('x' == c) {
+        if ('T' == c) {
             addConverter(new TraceIdPatternConverter());
         } else {
             super.finalizeConverter(c);