BUG/MINOR: cfgparse: Fix the call to post parser of the last sections parsed

Wrong variable was used to know if we need to call the callback
post_section_parser() or not. We must use 'cs' and not 'pcs'.

This patch must be backported in 1.8 with the commit 7805e2b ("BUG/MINOR:
cfgparse: Fix transition between 2 sections with the same name").
diff --git a/src/cfgparse.c b/src/cfgparse.c
index a28d24c..d754dd5 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -1890,8 +1890,8 @@
 			err_code |= pcs->post_section_parser();
 			if (err_code & ERR_ABORT)
 				goto err;
-			pcs = NULL;
 		}
+		pcs = NULL;
 
 		if (!cs) {
 			ha_alert("parsing [%s:%d]: unknown keyword '%s' out of section.\n", file, linenum, args[0]);
@@ -1903,7 +1903,7 @@
 		}
 	}
 
-	if (cs && pcs->post_section_parser)
+	if (cs && cs->post_section_parser)
 		err_code |= cs->post_section_parser();
 
 err: