Docker incorrectly assumes swappiness can't be more than 100

[SharkWipf]

Description
When passing the --swappiness flag to run or create with a value greater than 100, Docker will throw an error stating swappiness has to be between 0 and 100.
However, swappiness values above 100 are perfectly valid, and the swappiness setting is more than just a percentage knob.
Unless this is a limit in cgroups that isn't in-line with the kernel's own swappiness settings, Docker should accept swappiness values greater than 100 in line with the rest of the system.

Steps to reproduce the issue:

1. Run any docker create or docker run command with --swappiness=133

Describe the results you received:

docker: invalid value: 133. Valid memory swappiness range is 0-100.
See 'docker create --help'.

Describe the results you expected:
Container starts normally with the specified swappiness setting.

Output of docker version:

Client:
 Version:           19.03.13
 API version:       1.40
 Go version:        go1.15.2
 Git commit:        4484c46d9d
 Built:             Sun Sep 27 02:04:14 2020
 OS/Arch:           linux/amd64
 Experimental:      false

Server:
 Engine:
  Version:          19.03.13
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.15.2
  Git commit:       4484c46d9d
  Built:            Sun Sep 27 02:03:53 2020
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.3.7
  GitCommit:        8fba4e9a7d01810a393d5d25a3621dc101981175
 runc:
  Version:          1.0.0-rc10
  GitCommit:        dc9208a3303feef5b3839f4323d9beb36df0a9dd
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683b971d9c3ef73f284f176672c44b448662

Output of docker info:

N/A

[thaJeztah]

Thanks for reporting; the original pull request doesn't motivate why 0-100 was picked at the time #14004, so not sure if there was a reason for this. We'd have to check if changing the range will cause issues, but otherwise I see no direct reason to disallow this.

[thaJeztah]

/cc @AkihiroSuda