tools: console: pass stream/fd errors to user

tools: console: pass stream/fd errors to user

If the console was disconnected due to a connection problem or a problem on the
server side it is convinient to provide the cause to the user. If the error
come from the API then the error is saved in a virsh global variable. However,
since success is returned from virshRunConsole after we reach the waiting stage,
then the error is never reported. Let's track the error in the event loop.

Next after failure we do a cleanup and this cleanup can overwrite
root cause. Thus let's save root cause immediately and then set it to
virsh error after all cleanup is done.

Since we'll be sending the error to the consumer, each failure path from
the event handlers needs to be augmented to provide what error generated
the failure.

Reviewed-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>