pgsql: Fix random discrepancies between parallel_schedule and serial_sc

Fix random discrepancies between parallel_schedule and serial_schedule.

In particular, my previous patch expected the create_index test to run
before the inherit test; but this was only true in the serial schedule.
Rearrange this portion of the schedules to be more consistent.

Per buildfarm results.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/6d295b64945cb6ff9b64f55d1e51b5e2a1bb6f84

Modified Files
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src/test/regress/parallel_schedule |   12 ++++++++----
src/test/regress/serial_schedule   |   12 ++++++------
2 files changed, 14 insertions(+), 10 deletions(-)