Distributor setting is not respected when versioned feature flag is in effect

[ferki]

When a versioned feature flag is enabled, and a distributor is set, like:

use Rex -feature => ['1.4'];

set_distributor 'Parallel_ForkManager';

then the distributor setting does not seem to have any effect (in other words, it always loads Rex::TaskList::Base), as shown by the debug output:

$ rex -d uptime
[2020-04-07 20:01:44] DEBUG - This is Rex version: 1.9.0
[...]
[2020-04-07 20:01:44] DEBUG - activating featureset >= 0.51
[2020-04-07 20:01:44] DEBUG - activating featureset >= 0.40
[2020-04-07 20:01:44] DEBUG - activating featureset >= 0.35
[2020-04-07 20:01:44] DEBUG - activating featureset >= 0.31
[2020-04-07 20:01:44] DEBUG - Creating new distribution class of type: Base
[2020-04-07 20:01:44] DEBUG - new distribution class of type Rex::TaskList::Base created.
[2020-04-07 20:01:44] DEBUG - Returning existing distribution class of type: Rex::TaskList::Base
[2020-04-07 20:01:44] DEBUG - Creating task: uptime
[...]

On one hand this is because the Rex::TaskList creation is cached, so only one object is created (this is probably good), and on the other hand it's because activating the 0.31 feature set simply calls Rex::TaskList->create()->set_default_auth(0); which creates the object before any configuration options are considered.

I'll propose a fix in a PR soon, which converts the default_auth setting into a first-class configuration option, so 0.31 can behave exactly like other feature flags (that is, simply setting values for configuration variables, instead of instantiating objects early).