regression failure on master with --disable-integer-datetimes

Introduced in commit 4318daecc959886d001a6e79c6ea853e8b1dfb4b.

Attached regression failure and patch. It looks like we're no longer
running floating point timestamps on the buildfarm?

To make the output for float/integer timestamps the same, we either need
to remove the fractional seconds or reduce the number of hours.

It looks like the test is for maximum output length of an interval, so
it seems better to reduce the number of hours to one million, which is
what my patch does. It still loses 3 characters of output length, which
is a bit unfortunate given the purpose of the test, but it's better than
losing 7. I don't have a better idea.

Regards,
Jeff Davis