Init foreign modify state early like it's done in 6.6.0 (#73)

The changes made in 27b899d moved
initialization of fdw global state to later phase - from pxfBeginForeignModify()
to pxfExecForeignInsert(). This may break another projects which depend on pxf
fdw. The patch temporary restores old behavior.

fdw/pxf_fdw.c

@@ -610,6 +610,18 @@ pxfBeginForeignModify(ModifyTableState *mtstate,
 	 * external resource in the QD node, when all the actual insertions happen
 	 * in the segments.
 	 */
+	/* begin of temp block */
+	/*
+	 * Previously, ri_FdwState initialized here, but not in
+	 * pxfExecForeignInsert(). This was optimized, but unfortunately, there may
+	 * be some external projects that depend on old behavior. Here we do a temp
+	 * fix, which restores old behavior.
+	 */
+	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+		return;
+	if (!resultRelInfo->ri_FdwState)
+		resultRelInfo->ri_FdwState = InitForeignModify(resultRelInfo->ri_RelationDesc);
+	/* end of temp block */
 }
 
 /*