pgsql: Don't wait for the commit record to be replicated if we wrote no

Don't wait for the commit record to be replicated if we wrote no WAL.

When using synchronous replication, we waited for the commit record to be
replicated, but if we our transaction didn't write any other WAL records,
that's not required because we don't even flush the WAL locally to disk in
that case. This lead to long waits when committing a transaction that only
modified a temporary table. Bug spotted by Thom Brown.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/fe546f3da6a5ff1d879f587728f74ec457f0ee5f

Modified Files
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src/backend/access/transam/xact.c |    3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)