Add support for sh in shell command and fix indy-node-monitor image

[WadeBarnes]

• Fixes the issue shelling into the prometheus container.
• Fixes issue with plugins missing from the indy-node-monitor image.

Note:

• The main change was made to openShell. Everything else is whitespace additions or cleanup.

[WadeBarnes]

@lynnbendixsen, Please review. This fixes the issue you reported.