sample plugins: reduce code duplication across the sample plugins hosted in the core NRI repo. #250
Description
We host a set of sample and/or simple plugins in the core NRI repository, under the plugins directory tree. As the number of plugins slowly grows, there is an increasing amount of code duplication across these plugins. Most of it simply aims to keep some plugin-neutral NRI-specific aspects of the plugins identical, such as command line options for providing the plugin's identity, the possibility to override the default NRI socket location, etc. This is becoming error prone over time, and makes the plugins prone to divergence wrt. command line options and possibly other behavioral aspects which are supposed to be common but are not implemented by shared code.
The sample plugins should be refactored, distilling out common bits to a single shared code base then reimporting it to each plugin. Candidates for the shared location are plugins/common, or the already existing pkg/plugins.
See #249 (review) for the original related comment and possible follow-up discussion.