Call fdcloseexec right after fdunshare.

No functional changes.

MFC after:	1 week

sys/kern/kern_exec.c

@@ -595,6 +595,8 @@ interpret:
 	 * be shared after an exec.
 	 */
 	fdunshare(td);
+	/* close files on exec */
+	fdcloseexec(td);
 
 	/*
 	 * Malloc things before we need locks.
@@ -608,8 +610,6 @@ interpret:
 		bcopy(imgp->args->begin_argv, newargs->ar_args, i);
 	}
 
-	/* close files on exec */
-	fdcloseexec(td);
 	vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
 
 	/* Get a reference to the vnode prior to locking the proc */