Compare unlink dir error with syscall.EISDIR

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Merge pull request #27 from LK4D4/fix_unlink_error_check

Fix unlink error check
Implement truncate

Fixes bradfitz/docker#8

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Use reflection instead of proto.Clone.

proto.Clone is relatively expensive for making an empty message.

Docker-DCO-1.1-Signed-off-by: David Symonds <dsymonds@golang.org> (github: dsymonds)
Merge pull request #29 from dsymonds/fuse

Use reflection instead of proto.Clone.
Merge pull request #28 from LK4D4/implement_truncate_#8

Implement truncate
vfuse: check paths in all methods
Implement Mknod

Fixes bradfitz/docker#16
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)