gcode: process_batch() should execute commands atomically

Update the process_batch() method so that it will not interleave
commands read from the input fd with the batched commands.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/virtual_sdcard.py

@@ -164,7 +164,7 @@ class VirtualSD:
                 continue
             # Dispatch command
             try:
-                res = self.gcode.process_batch(lines[-1])
+                res = self.gcode.process_batch([lines[-1]])
                 if not res:
                     self.reactor.pause(self.reactor.monotonic() + 0.100)
                     continue