pgsql: Try to fix spurious DSM failures on Windows.

Try to fix spurious DSM failures on Windows.

Apparently, Windows can sometimes return an error code even when the
operation actually worked just fine.  Rearrange the order of checks
according to what appear to be the best practices in this area.

Amit Kapila

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/1a81daab8be9a0b3769a2660db44a56a6035e34a

Modified Files
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src/backend/storage/ipc/dsm_impl.c |   28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)