Add JBoss support through mount agent by ModuleClassloader. (#527)

- Change the classloader to locate the agent path in AgentPackagePath, from `SystemClassLoader` to AgentPackagePath's loader.

Author: rechardguo

CHANGES.md

@@ -14,6 +14,7 @@ Release Notes.
 * [Chore] Exclude org.checkerframework:checker-qual and com.google.j2objc:j2objc-annotations
 * [Chore] Exclude proto files in the generated jar
 * Fix Jedis-2.x plugin can not get host info in jedis 3.3.x+
+* Change the classloader to locate the agent path in AgentPackagePath, from `SystemClassLoader` to AgentPackagePath's loader.
 
 #### Documentation
 

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/boot/AgentPackagePath.java

@@ -49,7 +49,7 @@ public static boolean isPathFound() {
     private static File findPath() throws AgentPackageNotFoundException {
         String classResourcePath = AgentPackagePath.class.getName().replaceAll("\\.", "/") + ".class";
 
-        URL resource = ClassLoader.getSystemClassLoader().getResource(classResourcePath);
+        URL resource = AgentPackagePath.class.getClassLoader().getResource(classResourcePath);
         if (resource != null) {
             String urlString = resource.toString();