Switch file descriptors to non-blocking mode for sendfile
Switch file descriptors to non-blocking mode for sendfile

Sendfile requires file descriptors to be in blocking mode.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@citrix.com>

euanh/vhd-tool,euanh/vhd-tool,djs55/vhd-tool,djs55/vhd-tool,thomassa/vhd-tool