pgsql: Adjust time qual checking code so that we always check

Log Message:
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Adjust time qual checking code so that we always check TransactionIdIsInProgress
before we check commit/abort status.  Formerly this was done in some paths
but not all, with the result that a transaction might be considered
committed for some purposes before it became committed for others.
Per example found by Jan Wieck.

Modified Files:
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    pgsql/src/backend/utils/time:
        tqual.c (r1.87 -> r1.88)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/time/tqual.c.diff?r1=1.87&r2=1.88)