motion: fix brake/direction setting when S command is sent.

spindle_on command is also used for setting the spindle speed via S code.
Setting the S code does not mean the brake or direction should be changed if
M3/M4 is not active.

Ultimately we should have a separate set_spindle_speed_command to make
this cleaner

Author: c-morley

src/emc/motion/command.c

@@ -1609,12 +1609,14 @@ void emcmotCommandHandler_locked(void *arg, long servo_period)
 	        emcmotStatus->spindle_status[n].speed = emcmotCommand->vel;
 	        emcmotStatus->spindle_status[n].css_factor = emcmotCommand->ini_maxvel;
 	        emcmotStatus->spindle_status[n].xoffset = emcmotCommand->acc;
-	        if (emcmotCommand->vel >= 0) {
-		    emcmotStatus->spindle_status[n].direction = 1;
-	        } else {
-		    emcmotStatus->spindle_status[n].direction = -1;
-	        }
-	        emcmotStatus->spindle_status[n].brake = 0; //disengage brake
+            if (emcmotCommand->state) {
+	            if (emcmotCommand->vel >= 0) {
+		        emcmotStatus->spindle_status[n].direction = 1;
+	            } else {
+		        emcmotStatus->spindle_status[n].direction = -1;
+	            }
+	            emcmotStatus->spindle_status[n].brake = 0; //disengage brake
+            }
             apply_spindle_limits(&emcmotStatus->spindle_status[n]);
         }
         emcmotStatus->atspeed_next_feed = emcmotCommand->wait_for_spindle_at_speed;