Rebase to 2.3.4
    
    Remove test adjustments.
    Fixes mentioning GH#{11606,12362,12363} are present.
    
    Remove test adjustments for Ruby 2.7 compatibility.
    There is a much newer Ruby available in Fedora.
    
    Newer childprocess is present in Fedora for
    some time now. We can stop grepping for failures.
    
    Remove test adjustment for fake_ftp 0.3.0 compatibility.
    Not required anymore.
    
    Remove obsolete for vagrant-atomic that was retired in F26.
    
    Remove the net-ssh patch.
    It is not present anymore in the new version.
    And we are going to have net-ssh >= 7.