bin/bitbake: Only try and process an event_queue if it exists

The connection may have failed before the event queue has been setup.
Handle this correctly in the exception handler.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
server/xmlrpc: Simlify featureset handling

Rather than passing featureset around various places where the data doesn't
really belong, run a command at connection time to set the appropriate
features. This is similar to what the process server does.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>