version command should exit 0

Created by: mr-c

$ ./udocker version; echo Return code: $?
version: 1.1.1
tarball: https://owncloud.indigo-datacloud.eu/index.php/s/AFImjw8ii0X72xf/download https://cernbox.cern.ch/index.php/s/VC7GuVWA7mYRAiy/download http://repo.indigo-datacloud.eu/repository/indigo/2/centos7/x86_64/tgz/udocker-1.1.1.tar.gz
Return code: 1

$ docker version; echo Return code: $?
Client:
 Version:      17.05.0-ce
 API version:  1.29
 Go version:   go1.7.5
 Git commit:   89658be
 Built:        Thu May  4 22:09:06 2017
 OS/Arch:      linux/amd64

Server:
 Version:      17.05.0-ce
 API version:  1.29 (minimum version 1.12)
 Go version:   go1.7.5
 Git commit:   89658be
 Built:        Thu May  4 22:09:06 2017
 OS/Arch:      linux/amd64
 Experimental: false
Return code: 0