Clean up doc build so it doesn't stacktrace

Fixes #18471

- Add zmq.eventloop to mocked modules in doc/conf.py
- Cleaned up rst references in rest_tornado.rst
Check for blockDeviceMapping
Add lithium release notes
quote strs in virtualenv mod
doh!
Merge pull request #18494 from rallytime/cleanup_doc_build

Clean up doc build so it doesn't stacktrace
Merge pull request #18496 from basepi/lithiumnotes

Add lithium release notes stub
Start listening for events when RunnerClient is instantiated

If we're not listening to the eventstream before starting a new job
there's a high likelyhood that we'll miss the job return event. This
change mimics the event-based runners addition slated for Boron.
Move `cleanup_runtime_config_instance` out of TestDaemon
Use atexit for the cleanup
Merge pull request #18500 from s0undt3ch/develop

Move `cleanup_runtime_config_instance` out of TestDaemon
Whitespace fix
Merge pull request #18502 from rallytime/pylint_fix

Whitespace fix
Merge pull request #18499 from whiteinge/runner-sync-eventlisten

Start listening for events when RunnerClient is instantiated
Added special branch '_' in git_pillar to match saltenv
Renamed special branch from '_' to '__env__'
Merge branch 'develop' of github.com:keesbos/salt into develop
fixed pylint violations
Handle highstate output when the result is a dict
Properly output the results of salt.function states