_ci_: More tweaks to snapcraft release process

[ianconsolata]

Related Issues

Even after merging my previous PR, snapcraft publish failed again on the 1.17.0-rc4 release with ZeroDivisionError: integer division or modulo by zero.

Proposed Changes

1. We shouldn't be publishing to stable on RC tags, so instead publish to the candidate channel for RC releases.
2. When I ssh in the CircleCI build environment and run the exact same publish command, it works. So the only thing I can think might be the cause is the *.snap isn't matching the built file for some reason. So add extra verbose logging to the snap deploy job to figure out why it keeps erroring.

Checklist

Before you mark the PR ready for review, please make sure that:

• All commits have a clear commit message.
• The PR title is in the form of of <PR type>: <area>: <change being made>
  • example: fix: mempool: Introduce a cache for valid signatures
  • PR type: fix, feat, INTERFACE BREAKING CHANGE, CONSENSUS BREAKING, build, chore, ci, docs,perf, refactor, revert, style, test
  • area: api, chain, state, vm, data transfer, market, mempool, message, block production, multisig, networking, paychan, proving, sealing, wallet, deps
• This PR has tests for new functionality or change in behaviour
• If new user-facing features are introduced, clear usage guidelines and / or documentation updates should be included in https://lotus.filecoin.io or Discussion Tutorials.
• CI is green