PT-2340 - Support MySQL 8.4

- Added sleep to t/lib/MasterSlave.t, so it does not fail on fast machines
- Disabled SSL tests on versions earlier than 8.0

t/pt-stalk/ssl.t

@@ -25,6 +25,9 @@ my $dbh = $sb->get_dbh_for('source');
 if ( !$dbh ) {
    plan skip_all => 'Cannot connect to sandbox source';
 }
+elsif ( $sandbox_version lt '8.0' ) {
+   plan skip_all => "Requires MySQL 8.0 or newer";
+}
 
 my $cnf      = "/tmp/12345/my.sandbox.cnf";
 my $pid_file = "/tmp/pt-stalk.pid.$PID";