Add a NRPE check to monitor the number of threads connected
to the MySQL database, in proportion to the maximum number of connections.
For this check, a nagios user will be created. This user does not have any
permissions set, does not have access to any database and can only connect
from localhost.
Warning and Critical thresholds (in percentage) can be configured.
Add an action to reset nagios's password. This action could only be run
on the leader unit.
Closes-Bug: #1816759
Change-Id: Id35b0331322c2744a9f839b3eb153eed1bc53aac
11ee1ef563