MariaDB Monitor rebuild server may try to chown "/var/lib/mysql/" instead of just "/var/lib/mysql"

If rebuild target server is running, the monitor asks it where its datadir is with "select @@datadir;". This returns the directory with / at the end, and the value is used as is in later commands ("rm -rf <datadir>/*" and "chown -R mysql:mysql <datadir>". The latter command can fail if MaxScale does not have full sudo privs and instead the command is enabled with a sudoers.d-file with a line like "johnny ALL= NOPASSWD: /bin/chown -R mysql\:mysql /var/lib/mysql". The line is given in the documentation so may cause confusion.

To reduce chances of confusion, the documentation should include both:

johnny ALL= NOPASSWD: /bin/chown -R mysql\:mysql /var/lib/mysql

johnny ALL= NOPASSWD: /bin/chown -R mysql\:mysql /var/lib/mysql/

or perhaps alternatively

johnny ALL= NOPASSWD: /bin/chown -R mysql\:mysql /var/lib/mysql/*

The monitor should also remove the extra / from the directory returned by server.