Fixed case where header value contains a colon

Author: Nicolas Casaux

src/main/java/io/github/delirius325/jmeter/backendlistener/elasticsearch/ElasticSearchMetric.java

@@ -196,7 +196,7 @@ private void parseHeadersAsJsonProps(boolean allReqHeaders, boolean allResHeader
 
         for(String[] lines : headersArrayList) {
             for(int i=0; i < lines.length; i++) {
-                String[] header = lines[i].split(":");
+                String[] header = lines[i].split(":",2);
 
                 // if not all req headers and header contains special X-tag
                 if(header.length > 1) {