Extend mariadb-server to purge gracefully if datadir is a mountpoint (Closes: #829491)
Extend mariadb-server to purge gracefully if datadir is a mountpoint (Closes: #829491)

This will also
* not use the existence of lost+found as indicator for /var/lib/mysql
  being a mount point.
* to also keep erroneously renamed lost+found directories as they
  might continue to exist after a switch from MySQL to MariaDB.

ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0,ottok/mariadb-10.0