Beckhoff: velocity sometimes goes to 0

[rerpha]

This is caused by some issue in the velocity forwarding monitor (aka gets the velo from controller, then forwards to motor rec) - i am going to disable as agreed with the motion team.

Acceptance criteria

• jog and normal velocity are not forwarded to the motor record
• documentation for setting up a beckhoff re-includes setting velocities manually

[rerpha]

https://github.com/ISISComputingGroup/EPICS-ioc/pull/946/files
ISISComputingGroup/ibex_developers_manual#111
#8876

This is really more of a flash review than anything as it can't easily be tested.