Use separate buffers for stdout and stderr on executing git-lfs-authenticate
Use separate buffers for stdout and stderr on executing git-lfs-authenticate

It's fix authentication issue on ssh error messages like:
```
X11 forwarding request failed
```

Jericho25/-git-lfs_miilkyway,ryansimmen/git-lfs,dakotahawkins/git-lfs,bozaro/git-lfs,github/git-lfs,dakotahawkins/git-lfs,ttaylorr/git-lfs,ttaylorr/git-lfs,github/git-lfs,ryansimmen/git-lfs,aleb/git-lfs,Jericho25/-git-lfs_miilkyway,ttaylorr/git-lfs,github/git-lfs,larsxschneider/git-lfs,andyneff/git-lfs,andyneff/git-lfs,bozaro/git-lfs,bozaro/git-lfs,dakotahawkins/git-lfs,andyneff/git-lfs,Jericho25/-git-lfs_miilkyway,ryansimmen/git-lfs,aleb/git-lfs,larsxschneider/git-lfs,aleb/git-lfs,larsxschneider/git-lfs