A separate ticket has been filed for error message getting generated while disabling all plugins. This seems to be an isolated case pertinent to demo plugin only. Please see QA test steps for more detail.
1. Build demo plugin from master.
2. Install it in a MM instance.
3. Enable it, then disable.
4. Enable it again.
Expected: Enabling and disabling happens smoothly without error every time.
Observed: Plugin is enabled smoothly in step 3. In step 4, enabling generates > 50 lines of the following error:
`RPC call MessageHasBeenPosted to plugin failed. caller="mlog/log.go:174" error="connection is shut down" plugin_id=com.mattermost.demo-plugin`
No testing required.