Ensure ClassloadingInstrumentation is always applied even with DD_TRACE_ENABLED=false

This avoids potential class-loading delegation issues when using other products in dd-java-agent

Author: mcculls

dd-java-agent/instrumentation/classloading/src/main/java/datadog/trace/instrumentation/classloading/ClassloadingInstrumentation.java

@@ -16,6 +16,7 @@
 import datadog.trace.agent.tooling.InstrumenterModule;
 import datadog.trace.bootstrap.CallDepthThreadLocalMap;
 import datadog.trace.bootstrap.Constants;
+import java.util.Set;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.description.type.TypeDescription;
 import net.bytebuddy.matcher.ElementMatcher;
@@ -31,14 +32,19 @@
  * for the classes that we have put in the bootstrap class loader.
  */
 @AutoService(InstrumenterModule.class)
-public final class ClassloadingInstrumentation extends InstrumenterModule.Tracing
+public final class ClassloadingInstrumentation extends InstrumenterModule
     implements Instrumenter.ForBootstrap,
         Instrumenter.ForTypeHierarchy,
         Instrumenter.HasMethodAdvice {
   public ClassloadingInstrumentation() {
     super("classloading");
   }
 
+  @Override
+  public boolean isApplicable(Set<TargetSystem> enabledSystems) {
+    return true;
+  }
+
   @Override
   protected boolean defaultEnabled() {
     return true;