pysmurf-monitor: Enable metadata feed buffer

[BrianJKoopman]

Description

This PR enables the feed buffer for the pysmurf-monitor metadata feed(s).

Motivation and Context

This prevents the feed from publishing immediately, instead publishing 1/sec, which should reduce the load on the crossbar server. This is publishing around 150-200/sec in practice otherwise.

How Has This Been Tested?

I've tested this change while publishing as fast as I possibly can from a single thread on my laptop. The crossbar server CPU usage drops from essentially full (100%) usage to <1%.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.