tests: Eliminate ISO 8601 formatting workaround for dates

Follow up to commit
732017e4e5235e28c578cc3367fa0c4548b65495732017e4e5235e28c578cc3367fa0c4548b65495.

https://bugzilla.gnome.org/show_bug.cgi?id=739956
tests: Switch to non-interactive tests by default

This fixes `make check` stalling forever on requesting user input. To
run the interactive tests, the programs now need to be run with
--interactive.