vdagent: Reset properly state of pending large messages upon disconnection
If the client closes the connection while having pending large messages (split into multiple chunks) the state is not correctly reset causing next client messages to be not correctly handled.
This can occur for instance if the client is closed (or killed) while transferring a large file.
This fixes https://bugzilla.redhat.com/show_bug.cgi?id=1548419.
Signed-off-by: Frediano Ziglio freddy77@gmail.com