Fix incorrect error message and method call on ComponentRpm
    
    When resubmitting a module build, if some component is found out that
    its attributes have changed, MBS will raise an error to stop the work to
    recording components. The problem is original code tells a module build
    exists in database already rather than a component build, meanwhile
    get_module_name() call on an ComponentRpm object is also incorrect.
    
    Signed-off-by: Chenxiong Qi <cqi@redhat.com>