Improve percona cluster initialization

* Switch from /etc/init.d/mysql bootstrap-pxc to
  /etc/init.d/mysql restart-bootstrap when bootstrapping
  a new cluster. This ensures that, even when Percona starts
  at boot, that new config is loaded and the cluster is
  bootstrapped.

* If percona fails to bootstrap or restart, ensure we do not
  touch the initialized file, allowing os-refresh-config to
  try again on the next iteration.

Co-Authored-By: Gregory Haynes <greg@greghaynes.net>
Change-Id: Ia720e40329a1d39db2e25fc917fbf5b5ea85dedc
Merge "Improve percona cluster initialization"