pgsql: Add TAP tests for 2PC post-commit callbacks of multixacts atrec

Add TAP tests for 2PC post-commit callbacks of multixacts at recovery

The current set of TAP tests for two-phase transactions include some
coverage for post-commit callbacks of multixact, but it lacked tests for
testing the recovery of those callbacks.  This commit adds some tests
with soft and hard restarts in this case, using transactions which
include DDLs.

Author: Michael Paquier
Reviewed-by: Oleksii Kliukin
Discussion: https://postgr.es/m/20190221055431.GO15532@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b1086767087efe437131b9059fc6f2d3b7c7ecc2

Modified Files
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src/test/recovery/t/009_twophase.pl | 56 ++++++++++++++++++++++++++++++++++++-
1 file changed, 55 insertions(+), 1 deletion(-)