check_replica_set false positives

[Laurent Sesquès]

Since https://code.launchpad.net/~peter-sabaini/charm-mongodb/+git/charm-mongodb/+merge/396580, the charm sets up a check for replica set:

+ name = get_replica_set_name()
[...]
+ mongo_res = get_cmd_result(
+ ["/usr/bin/mongo", name, "--quiet", "--eval", "JSON.stringify(rs.status())"]
+ )

This only works if we chose a replicaset value that corresponds to a host on which this mongodb is running.

I think that this check should be replaced with something like:
host, port, replicaset = get_mongo_details()
mongo_res = get_cmd_result(
    ["/usr/bin/mongo", "{}:{}".format(host, port), "--quiet", "--eval", "JSON.stringify(rs.status('{}'.format(replicaset)))"]

Also, the check name should be updated with:
- shortname="check_replica_sets",
+ shortname="replica_sets",
Because the check name is automatically prepended with 'check_', currently leading to:

$ grep check_replica_sets /etc/nagios/nrpe.d/*check_replica_sets*
# check check_replica_sets
command[check_check_replica_sets]=/usr/local/lib/nagios/plugins/check_replica_sets.py

And finalyy of course, the tests should be updated to catch this issue.