[wpilib] DataLogManager: Use logs subdirectory on USB drives (#5975)

wpilibj/src/main/java/edu/wpi/first/wpilibj/DataLogManager.java

@@ -214,7 +214,10 @@ public final class DataLogManager {
         // prefer a mounted USB drive if one is accessible
         Path usbDir = Paths.get("/u").toRealPath();
         if (Files.isWritable(usbDir)) {
-          return usbDir.toString();
+          if (!new File("/u/logs").mkdir()) {
+            // ignored
+          }
+          return "/u/logs";
         }
       } catch (IOException ex) {
         // ignored