pgsql: Eschew "RESET statement_timeout" in tests.

Eschew "RESET statement_timeout" in tests.

Instead, use transaction abort.  Given an unlucky bout of latency, the
timeout would cancel the RESET itself.  Buildfarm members gharial,
lapwing, mereswine, shearwater, and sungazer witness that.  Back-patch
to 9.1 (all supported versions).  The query_canceled test still could
timeout before entering its subtransaction; for whatever reason, that
has yet to happen on the buildfarm.

Branch
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REL9_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/934fdaaca80e981dac90cdd974f61e7d493a78bf

Modified Files
--------------
src/test/regress/expected/plpgsql.out          |   43 ++++++++++++++++--------
src/test/regress/expected/prepared_xacts.out   |    6 ++--
src/test/regress/expected/prepared_xacts_1.out |    6 ++--
src/test/regress/sql/plpgsql.sql               |   37 +++++++++++++-------
src/test/regress/sql/prepared_xacts.sql        |    6 ++--
5 files changed, 65 insertions(+), 33 deletions(-)