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-kill/ssl.t

@@ -26,6 +26,9 @@ my $source_dbh = $sb->get_dbh_for('source');
 if ( !$source_dbh ) {
    plan skip_all => 'Cannot connect to sandbox source';
 }
+elsif ( $sandbox_version lt '8.0' ) {
+   plan skip_all => "Requires MySQL 8.0 or newer";
+}
 else {
    plan tests => 6;
 }