SEC-3031: DelegatingSecurityContext(Runnable|Callable) only modify SecurityContext on new Thread

Modifying the SecurityContext on the same Thread can cause issues. For example, with a
RejectedExecutionHandler the SecurityContext may be cleared out on the original Thread.

This change modifies both the DelegatingSecurityContextRunnable and DelegatingSecurityContextCallable to,
by default, only modify the SecurityContext if they are invoked on a new Thread. The behavior can be changed
by setting the property enableOnOrigionalThread to true.

web/src/test/java/org/springframework/security/web/servletapi/SecurityContextHolderAwareRequestFilterTests.java

@@ -321,7 +321,7 @@ public class SecurityContextHolderAwareRequestFilterTests {
 				.getValue();
 		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, SecurityContext.class))
 				.isEqualTo(context);
-		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, Runnable.class))
+		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, "delegate"))
 				.isEqualTo(runnable);
 	}
 
@@ -348,7 +348,7 @@ public class SecurityContextHolderAwareRequestFilterTests {
 				.getValue();
 		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, SecurityContext.class))
 				.isEqualTo(context);
-		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, Runnable.class))
+		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, "delegate"))
 				.isEqualTo(runnable);
 	}
 
@@ -375,7 +375,7 @@ public class SecurityContextHolderAwareRequestFilterTests {
 				.getValue();
 		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, SecurityContext.class))
 				.isEqualTo(context);
-		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, Runnable.class))
+		assertThat(WhiteboxImpl.getInternalState(wrappedRunnable, "delegate"))
 				.isEqualTo(runnable);
 	}