t7800: broken quoting of looped test bodies
SZEDER made me aware of a quoting issue with some test refactorings in t7800 I recently introduced when refactoring the tests to run in a loop. This patch series fixes those issues and also adds a paragraph to "t/README" to document how this is supposed to be done properly.
Closes t7800: broken quoting of looped test bodies (#283 - closed).