Adjust WMAgent configuration such that it keeps less work in its queue

[amaltaro]

Impact of the new feature
WMAgent

Is your feature request related to a problem? Please describe.
The idea is not to keep a too large backlog in the agent's queue: jobs to be created, jobs created, jobs pending; such that badly behaving workflows - especially with respect to very short jobs - don't crash the agents and/or blow up component's duty cycle.

Describe the solution you'd like
Making up a reasonable enough number, I would say keeping between 50-70k jobs pending in the condor queue (and nothing else queued in local workqueue and/or in created status) would be a good commitment.

This can be achieved by tweaking one - or both - WorkQueueManager parameters:
https://github.com/dmwm/WMCore/blob/a63cf47/etc/WMAgentConfig.py#L147-L148

or the AgentStatusWatcher pending attributes:
https://github.com/dmwm/WMCore/blob/a63cf47/etc/WMAgentConfig.py#L355-L356

Note that for AgentStatusWatcher attributes, the actual thresholds are weighted according to the number of agents connected t the same team name (the more agents share the same team, the smaller those pending thresholds are).

Describe alternatives you've considered
We will probably have to test out a few different configurations with a production scenario, hence with 4 or 5 agents connected to the same team name.

Additional context
None