SEC-1578: Use ThreadLocal.remove() instead of ThreadLocal.set(null)

core/src/main/java/org/springframework/security/core/context/InheritableThreadLocalSecurityContextHolderStrategy.java

@@ -35,7 +35,7 @@ final class InheritableThreadLocalSecurityContextHolderStrategy implements Secur
     //~ Methods ========================================================================================================
 
     public void clearContext() {
-        contextHolder.set(null);
+        contextHolder.remove();
     }
 
     public SecurityContext getContext() {

core/src/main/java/org/springframework/security/core/context/ThreadLocalSecurityContextHolderStrategy.java

@@ -34,7 +34,7 @@ final class ThreadLocalSecurityContextHolderStrategy implements SecurityContextH
     //~ Methods ========================================================================================================
 
     public void clearContext() {
-        contextHolder.set(null);
+        contextHolder.remove();
     }
 
     public SecurityContext getContext() {