chore(graph/graph): remove dead code

This code was introduced with commented out sections. Just delete them.

Original commit: 18fc707fdf06aeb50fa5250f59f0ef4597d7cf73

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
Use Timeout Conn wrapper to set read deadline for downloading layer

Docker-DCO-1.1-Signed-off-by: Derek <crq@kernel.org> (github: crquan)
Handle EBUSY on remount

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add ErrPrerequisites to improve misleading errors

There are two cases where we can't use a graphdriver:

1) the graphdriver itself isn't supported by the system
2) the graphdriver is supported by some configuration/prerequisites are
missing

This introduces a new error for the 2) case and uses it when trying to
run docker with btrfs backend on a non-btrfs filesystem.

Docker-DCO-1.1-Signed-off-by: Johannes 'fish' Ziemke <github@freigeist.org> (github: discordianfish)
Merge pull request #6098 from crosbymichael/retry-mount

Handle EBUSY on remount
Merge pull request #6106 from discordianfish/improve-error-btrfs-on-non-btrfs

Add ErrPrerequisites to improve misleading errors
Merge pull request #6105 from gdm85/master

Do not consider iptables' output an error in case of xtables lock
Added a new method cgroups.GetStats() which will return a cgroups.Stats object which will contain all the available cgroup Stats.
Remove old Stats interface in libcontainers cgroups package.
Changed Stats to use unit64 instead of int64 to prevent integer overflow issues.
Updated unit tests.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Merge pull request #6096 from vishh/stats_strongtype

Replaced fs.Stats() interface with fs.GetStats() which returns a cgroups.Stats strong type
Merge pull request #6048 from crquan/use-timeout-conn

Use Timeout Conn wrapper to set read deadline for downloading layer
block aufs on incompatible file systems

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #6109 from unclejack/block_aufs_on_top_of_btrfs

block aufs on incompatible file systems
Merge pull request #5855 from philips/remove-dead-code

chore(graph/graph): remove dead code