Munin contributed plugins

add proxmox_vm_count plugin (#1251)

Count the number of running virtual machines in a proxmox environment.

zfs list -t filesystem,volume to suppress snapshots

zfs list might list a bunch of transient snapshots if `zpool
listsnapshots=on` and something like zfs-auto-snapshot is used. It's
also not useful to graph them since they're unchanging in time, and
the parent volume is graphed anyway. Limit zfs list to...

unit: add new plugin to monitor nginx unit app server

This multigraph plugin does basic monitoring of unit's applications.
See: https://unit.nginx.org/

systemd_mem: fix handling unlimited number on debian stretch

systemd_mem: add warning and critical from systemd config

fronius: support jq builds without math library

"round" is part of jq's math support. Some distros (rhel8) don't enable it.
Fortunately round can be emulated with "floor" which is always present in
modern jq.

Plugin dovecot: remove usage of "expr"

The usage of "expr" can be replaced easily with a shell builtin.
"expr" caused problems due to its hard-coded path.

Closes: #1240

plugin rsnapshot_duration: avoid "broken pipe" errors from tac

Consume the complete input from "tac". Otherwise spammy error messages
would appear in the log.

Fix switchbotmeter for pullreq https://github.com/munin-monitoring/contrib/pull/1236

Merge pull request #1235 from kmkr/master

Improve code readability and consistency

Reformat deluge_ with black and flake8

Improve code readability and consistency

This commit:

- Changes to Python 3 template string rather than the formatted string
syntax.
- Calls the Deluge API once per plugin run for the "states" mode, rather
than once per torrent. Lines of code are reduced. The readability is...

Plugin pacman_pending_updates: handle absence of available updates properly

"checkupdates" returns the exit code 2, if no updates are pending.
Previously the plugin did not output anything in this case.

Closes: #1233

Merge pull request #1058 from jtsage/add-template-munstrap4

Add "munstrap4" template.

rtom_vol: remove unused config parameters

Since there are no associated values for 'hashing', 'seeding', and
'active', a warning is seen in munin-update.log every time this plugin
is fetched.

bind9_*_stats: fix using env variable stat_file

previously only stat_file would only be used for data cleanup not for
fetching the data. also fixed some shellcheck warnings.

Merge pull request #1221 from shtrom/snmp__if_combined-stacked

Snmp if combined stacked

[snmp__if_combined] Add support for stacked series in root graph

From a summary comment in the code:

If a stacked graph is requested, plot the total. Rather than
    aggregating them with CDEFs of SUMs, we sum them in the script, which
    allows us to create real series than can be easily borrowed by other...

[snmp__if_combined] Fix issue with extrainfo

It was not collected / shown in the right spot, resulting in incorrect
information being shown.

Signed-off-by: Olivier Mehani <shtrom@ssji.net>

[snmp__if_combined] use snmp v2 description for root traffic graph

Signed-off-by: Olivier Mehani <shtrom@ssji.net>

[wunderground_] loan from other graphs in root

Signed-off-by: Olivier Mehani <shtrom@ssji.net>

Merge pull request #1206 from kimheino/amavis-guap

amavis_multi: multigraph plugin to monitor amavis mail filter

Fix pod doc in header of file

Merge pull request #1217 from Wicloz/patch-1 (improve debian/debsecan_ plugin)

Add suggest capabilities to the debian/debsecan_ plugin.

Refactor script to pure POSIX sh compliance.

Also includes recommended fixes