pgsql: Fix mishandling of background worker PGPROCs in EXEC_BACKEND bui

Fix mishandling of background worker PGPROCs in EXEC_BACKEND builds.

InitProcess() relies on IsBackgroundWorker to decide whether the PGPROC
for a new backend should be taken from ProcGlobal's freeProcs or from
bgworkerFreeProcs.  In EXEC_BACKEND builds, InitProcess() is called
sooner than in non-EXEC_BACKEND builds, and IsBackgroundWorker wasn't
getting initialized soon enough.

Report by Noah Misch.  Diagnosis and fix by me.

Branch
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REL9_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/aeebacff114634ffa07b5299ee6c41b219717bc3

Modified Files
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src/backend/postmaster/postmaster.c |    3 +++
1 file changed, 3 insertions(+)