Retry osquery instance launch until successful or shutdown requested

[RebeccaMahany]

Closes #1937

When the osquery runner cannot launch an osquery instance, we currently return an error, which will shut down launcher entirely.

Looking over the logs and past issues we've investigated, I saw two primary errors: 1) timeout waiting for osqueryd to create socket, indicating the osquery process did not start up, and 2) could not create an extension client where the socket file does not exist or the connection is refused.

In both of these cases, restarting launcher is overkill, and even detrimental to solving the issue. In some cases, we can see these errors happen when the current osquery version is old and not compatible with the current database; restarting launcher in this case is actively harmful because it resets the autoupdate delay, preventing a newer osquery version from being downloaded.

Instead, this PR implements retrying osquery instance launch until successful (or shutdown is requested).

I originally also wanted to implement If osquery instance launch fails, also consider triggering an autoupdate check for osquery. However, I realized this part of the criteria will be significantly easier to implement once #1412 is complete, so I'm putting it off for now.