Miscellaneous fixes to userspace Gridware

[jamesremuscat]

This PR includes various fixes and enhancements to userspace Gridware as detailed at https://alces.slack.com/files/U025J03R1/F6LLM7LTA/Personal_Gridware_notes.

A list of acceptance tests for these changes can be found at https://docs.google.com/document/d/1Rf25IsFYhNeck-FgxeFhRxT1KNGFYwRGyHhRmHEiHsQ.

(Both links are internal to Alces.)

Related PRs:

• clusterware-services: https://github.com/alces-software/clusterware-services/pull/58
• clusterware-handlers: https://github.com/alces-software/clusterware-handlers/pull/85
• flight-appliance-docs: https://github.com/alces-software/flight-appliance-docs/pull/69

[jamesremuscat]

To address a couple of the other comments/questions in the linked Slack document:

• Module loading is going to be slower since it has to verify and if necessary install distro dependencies, which means calling out to yum. In the "install" case this could take a little while.
• al gr requests install did accept --yes to install all without prompting; I've added an explicit option to the interactive mode.
  • As suggested by "no matching package found", the failure to load modules on a compute node was because of the earlier issue where the Gridware index didn't update at boot-time, so Gridware was unable to find the package definition to identify its dependencies.

Currently working on updating the documentation and will raise a PR in https://github.com/alces-software/flight-appliance-docs when that's done.