pgsql: Fix some more regression test row-order-instability issues.

Fix some more regression test row-order-instability issues.

Commit 0563a3a8b just introduced another instance of the same unsafe
testing methodology that appeared in 2ac3ef7a0, which I corrected in
257d81572. Robert/Amit, please stop doing that.

Also look through the rest of f0e44751d's test cases, and correct some
other queries with underdetermined ordering of results from the system
catalogs. These haven't failed in the buildfarm yet, but I don't
have any confidence in that staying true.

Per multiple buildfarm members.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/5ad966ab1c50e829462f2b3e3ffa59e2d95479e6

Modified Files
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src/test/regress/expected/alter_table.out | 3 ++-
src/test/regress/expected/create_table.out | 8 ++++++--
src/test/regress/sql/alter_table.sql | 3 ++-
src/test/regress/sql/create_table.sql | 8 ++++++--
4 files changed, 16 insertions(+), 6 deletions(-)