Enable forkCount of 1C in log4j-api tests

Signed-off-by: Matt Sicker <boards@gmail.com>
diff --git a/log4j-api/pom.xml b/log4j-api/pom.xml
index e08dca6..dcf060d 100644
--- a/log4j-api/pom.xml
+++ b/log4j-api/pom.xml
@@ -174,6 +174,7 @@
               junit.jupiter.execution.parallel.mode.default = concurrent
             </configurationParameters>
           </properties>
+          <forkCount>1C</forkCount>
           <reuseForks>true</reuseForks>
           <redirectTestOutputToFile>true</redirectTestOutputToFile>
           <excludedGroups>performance,smoke</excludedGroups>
diff --git a/log4j-api/src/test/java/org/apache/logging/log4j/LogManagerTest.java b/log4j-api/src/test/java/org/apache/logging/log4j/LogManagerTest.java
index 0b10b5b..c768118 100644
--- a/log4j-api/src/test/java/org/apache/logging/log4j/LogManagerTest.java
+++ b/log4j-api/src/test/java/org/apache/logging/log4j/LogManagerTest.java
@@ -21,6 +21,7 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.parallel.ResourceAccessMode;
 import org.junit.jupiter.api.parallel.ResourceLock;
+import org.junit.jupiter.api.parallel.Resources;
 
 import java.io.Closeable;
 import java.io.IOException;
@@ -28,7 +29,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
-@ResourceLock(value = "log4j2.LoggerContextFactory", mode = ResourceAccessMode.READ)
+@ResourceLock(value = Resources.SYSTEM_PROPERTIES, mode = ResourceAccessMode.READ)
 public class LogManagerTest {
 
     @SuppressWarnings("InnerClassMayBeStatic")
diff --git a/log4j-api/src/test/java/org/apache/logging/log4j/simple/SimpleLoggerTest.java b/log4j-api/src/test/java/org/apache/logging/log4j/simple/SimpleLoggerTest.java
index 9cd4043..4f144ac 100644
--- a/log4j-api/src/test/java/org/apache/logging/log4j/simple/SimpleLoggerTest.java
+++ b/log4j-api/src/test/java/org/apache/logging/log4j/simple/SimpleLoggerTest.java
@@ -23,9 +23,10 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.api.parallel.ResourceLock;
+import org.junit.jupiter.api.parallel.Resources;
 
 @Tag("smoke")
-@ResourceLock("log4j2.LoggerContextFactory")
+@ResourceLock(Resources.SYSTEM_PROPERTIES)
 public class SimpleLoggerTest {
 
     @RegisterExtension
diff --git a/log4j-api/src/test/java/org/apache/logging/log4j/util/Unbox2ConfigurableTest.java b/log4j-api/src/test/java/org/apache/logging/log4j/util/Unbox2ConfigurableTest.java
index fc25bca..cf4376f 100644
--- a/log4j-api/src/test/java/org/apache/logging/log4j/util/Unbox2ConfigurableTest.java
+++ b/log4j-api/src/test/java/org/apache/logging/log4j/util/Unbox2ConfigurableTest.java
@@ -20,6 +20,7 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.EnabledIfSystemProperty;
+import org.junit.jupiter.api.parallel.Isolated;
 import org.junit.jupiter.api.parallel.ResourceLock;
 import org.junit.jupiter.api.parallel.Resources;
 
@@ -35,7 +36,7 @@
  * enable the test, too.
  */
 @EnabledIfSystemProperty(named = "test", matches = ".*Unbox2ConfigurableTest.*")
-@ResourceLock(Resources.SYSTEM_PROPERTIES)
+@Isolated
 public class Unbox2ConfigurableTest {
     @BeforeAll
     public static void beforeClass() {