pgsql: Fix parallel index builds for dynamic_shared_memory_type=none.

Fix parallel index builds for dynamic_shared_memory_type=none.

The previous code failed to realize that this setting effectively
disables parallelism, and would crash if it decided to attempt
parallelism anyway.  Instead, treat it as a disabling condition.

Kyotaro Horiguchi, who also reported the issue. Reviewed by Michael
Paquier and Peter Geoghegan.

Discussion: http://postgr.es/m/20180209.170635.256350357.horiguchi.kyotaro@lab.ntt.co.jp

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/88ef48c1ccee6a2200e01318180cf521413b3012

Modified Files
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src/backend/optimizer/plan/planner.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)