repoclosure: Parse all fus logs
    
    Originally the list of solvables for fus was growing with each iteration
    and nothing was ever removed. That later changed so that fus iterations
    are only done on newly added stuff. It's great for performance, but
    means that the last log is not a superset of all others.
    
    To get all dependency problems we need to look into all log files, not
    just the last one.
    
    JIRA: COMPOSE-3964
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>