Add some suppressions that were missing. They are for if a STOP SLAVE is
executed early during IO thread startup, when it is negotiating with the
master. The master connection may be killed in the middle of a
mysql_real_query(), which is not a test failure if it is a network error.

This also caught one real code error, fixed with this commit: The I/O thread
would fail to automatically reconnect if a network error happened while
fetching the value of @@GLOBAL.gtid_domain_id.