worker_spi: Call pgstat_report_stat.

Without this, statistics changes accumulated by the worker never get
reported to the stats collector, which is bad.

Julien Rouhaud

src/test/modules/worker_spi/worker_spi.c

@@ -292,6 +292,7 @@ worker_spi_main(Datum main_arg)
 		SPI_finish();
 		PopActiveSnapshot();
 		CommitTransactionCommand();
+		pgstat_report_stat(false);
 		pgstat_report_activity(STATE_IDLE, NULL);
 	}