Use fixed period for update call of controller manager

[hartmanndennis]

PR for my suggestion in #126

Tested on KR5 with KRC4 and RSI 3.3 and it works very well both with IPO and IPO_FAST.

There is a problem with RSI 2.3 on KRC2 though. Here, IPOC gets increased by 1 instead of the cycletime of 12ms. Maybe I could use the check in kuka_hardware_interface.cpp

// Drop empty <rob> frame with RSI <= 2.3
  if (bytes < 100)
  {
    bytes = server_->recv(in_buffer_);
  }

to check for KRC2 and multiply the duration by 12 in this case?

[hartmanndennis]

The workaround works for me with RSI 2.3.

[gavanderhoorn]

We're having some problems with our KR210 here, so I can't really test this.

If someone else from the regulars here would care to test this PR, that would be greatly appreciated.