[LinuxCNC/linuxcnc Issue#558] MPG jog-counts acumulated in MDI mode cause motion when switching to Manual

Here are the steps I follow to reproduce the issue:

A MPG is needed to reproduce this issue.

1. Launch gmoccapy and home
2. Switch to MDI mode by clicking the MDI button on the right
3. Spin the MPG jog wheel to accumulate counts (no motion will occur)
4. Switch to manual mode (motion equivalent to the accumulated counts may occur)
5. If no motion occurred, it may be necessary to repeat steps 2 thru 4 several times

This is what I expected to happen:

Any MPG input when in MDI and Auto mode to be ignored

This is what happened instead:

MPG input while in MDI mode causes motion when mode is set to Manual

Observations:

It is intermittent, in that motion does not always occur, or at least it is not always noticeable. On my machine it seems to be more pronounced and happen more often on the Y and Z axes than on X.

Here is a video demonstrating the issue: https://youtu.be/GzDf7TJPEd4

It worked properly before this:

Unknown

Information about my hardware and software:

* I am using this Linux distribution and version: r12 Debian 9 (stretch) ISO
* I am running: Latest master from buildbot
* I am using this user interface: easily reproducible with gmoccapy, BP Touch
* I am using this interface hardware vendor and chipset: 7i76 encoder counter for MPG