Fix return value of pg_reload_conf() database utility function

Would always return "false", but as the value wasn't used anywhere,
the issue was inconsequential.

However while we're at it, actually check the return value in the
two places it's called, to help diagnose any issues in the unlikely
event they occur.

Per issue reported via GitHub PR #671 from user duzhgg.

dbutils.c

@@ -1255,7 +1255,7 @@ bool
 pg_reload_conf(PGconn *conn)
 {
 	PGresult   *res = NULL;
-	bool		success = false;
+	bool		success = true;
 
 	res = PQexec(conn, "SELECT pg_catalog.pg_reload_conf()");