Fix Unexpected error while reading stable configuration in tests

Author: ygree

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/Constants.java

@@ -15,6 +15,7 @@ public final class Constants {
    */
   public static final String[] BOOTSTRAP_PACKAGE_PREFIXES = {
     "datadog.slf4j",
+    "datadog.common.filesystem",
     "datadog.context",
     "datadog.environment",
     "datadog.json",

dd-java-agent/instrumentation-testing/src/main/java/datadog/trace/agent/test/BootstrapClasspathSetupListener.java

@@ -62,6 +62,7 @@ public void launcherSessionOpened(LauncherSession session) {
    */
   public static final String[] BOOTSTRAP_PACKAGE_PREFIXES_COPY = {
     "datadog.slf4j",
+    "datadog.common.filesystem",
     "datadog.context",
     "datadog.environment",
     "datadog.json",