This fixes few cases where driver eventor goroutines are leaked during
normal operations, but especially so in tests.
This change makes few modifications:
First, it switches drivers to use `Context`s to manage shutdown events.
Previously, it relied on callers invoking `.Shutdown()` function that is
specific to internal drivers only and require casting. Using `Contexts`
provide a consistent idiomatic way to manage lifecycle for both internal
and external drivers.
Also, I discovered few places where we don't clean up a temporary driver
instance in the plugin catalog code, where we dispense a driver to
inspect and validate the schema config without properly cleaning it up.
Fix some docstring typos and fix noisy log message during client restarts.
A log for the common case where the plugin socket isn't ready yet
isn't actionable by the operator so having it at info is just noise.
At shutdown, driver manager context expires and the fingerprinting
channel closes. Thus it is undeterministic which clause of The select
statement gets executed, and we may keep retrying until the
`i.ctx.Done()` block is executed.
Here, we check always check ctx expiration before retrying again.
Noticed that `detected drivers` log line was misleading - when a driver
doesn't fingerprint before timeout, their health status is empty string
`""` which we would mark as detected.
Now, we log all drivers along with their state to ease driver
fingerprint debugging.
The driver manager is modeled after the device manager and is started by the client.
It's responsible for handling driver lifecycle and reattachment state, as well as
processing the incomming fingerprint and task events from each driver. The mananger
exposes a method for registering event handlers for task events that is used by the
task runner to update the server when a task has been updated with an event.
Since driver fingerprinting has been implemented by the driver manager, it is no
longer needed in the fingerprint mananger and has been removed.
