smysql: stop explicity setting MYSQL_OPT_RECONNECT to 0

Setting this option, even to 0, causes spurious warnings to the console
with recent libmysqlclient versions. The upstream bug
( https://bugs.mysql.com/bug.php?id=112089 )
has now been open for a month, so we're implementing a workaround.

0 was the default since at least MySQL 5.7, perhaps longer.

closes PowerDNS#13242

(cherry picked from commit f1cbc20)

modules/gmysqlbackend/smysql.cc

@@ -489,11 +489,6 @@ void SMySQL::connect()
 
   do {
 
-#if MYSQL_VERSION_ID >= 50013
-    my_bool set_reconnect = 0;
-    mysql_options(&d_db, MYSQL_OPT_RECONNECT, &set_reconnect);
-#endif
-
 #if MYSQL_VERSION_ID >= 50100
     if (d_timeout) {
       mysql_options(&d_db, MYSQL_OPT_READ_TIMEOUT, &d_timeout);