Fix the limit command on aggregate pipeline.
Fix the limit command on aggregate pipeline.

  * Since it is a pipeline, the limit must happen after the group
    operation.

Change-Id: I16ad593e258571946b1d4c11f70b78883d9878ed

joyxu/kernelci-backend,joyxu/kernelci-backend,joyxu/kernelci-backend,kernelci/kernelci-backend,kernelci/kernelci-backend