virsh: respect -q/--quiet more
    
    Turn various vshPrint() informative messages into vshPrintExtra(), so
    they are not printed when requesting the quiet mode; neither XML/info
    outputs nor the results of commands are affected.
    Also change the expected outputs of the virsh-undefine test, since virsh
    is invoked in quiet mode there.
    
    Some informative messages might still be converted (and thus silenced
    when in quiet mode), but this is an improvements nonetheless.
    
    Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1358179