Change MSA reports type to be single select

Previously the report type was a multi select which was incorrect. This
commit changes it and also changes the tests to reflect this update.

I've also added a form-control class on the input which
increases the width to match with the rest of the form.
Single selects now same width as other input

Previously single selects were tiny compared to the rest of the inputs.
This commit increases the width to match the other inputs.
Merge pull request #328 from alphagov/fix-msa-report-types

Fix MSA report types and increase single select form widths