Unable to cancel batch in ISIS Reflectometry GUI

[rbauststfc]

Describe the bug

Clicking the pause button when processing a batch in the ISIS Reflectometry GUI no longer stops the batch reduction - it continues through to the end.

To Reproduce

1. Go to Interfaces -> Reflectometry -> ISIS Reflectometry
2. On the Runs tab, enter Investigation Id 1120015 and Cycle 11_3 and click the Search button.
3. Select several rows (from the ones not highlighted blue) and click the Transfer button to move them into the runs table on the right hand side.
4. Click the Process button above the table. This should start reducing all rows in the table and will enable the Pause button that is just to the right of it.
5. Click the Pause button. The processing will just continue as before until all rows are reduced.

Expected behavior

The batch processing should stop when the pause button is clicked. If an algorithm (row) is in the middle of the reduction then this should complete first, but no further rows should be processed.

Platform/Version (please complete the following information):

• Mantid Version - first introduced in version 6.8