backport: skip root requirement for ignite version

[chanwit]

(cherry picked from commit ec2f8f8)
Signed-off-by: Chanwit Kaewkasi chanwit@gmail.com

Resolved Conflicts:
cmd/ignite/cmd/root.go
cmd/ignite/ignite.go

Confirmed Result:

$ bin/ignite version
Ignite version: version.Info{Major:"0", Minor:"5+", GitVersion:"v0.5.2-1+c659a34acc2a73", GitCommit:"c659a34acc2a7331c6a500ada511993954694a8a", GitTreeState:"clean", BuildDate:"2019-09-16T14:03:04Z", GoVersion:"go1.12.6", Compiler:"gc", Platform:"linux/amd64"}
Firecracker version: v0.17.0
$ bin/ignite run weaveworks/ignite-ubuntu --ssh
FATA[0000] This program needs to run as root.           
$ sudo bin/ignite run weaveworks/ignite-ubuntu --ssh
[sudo] password for chanwit: 
INFO[0009] Created VM with ID "84dcb6201bca1467" and name "damp-flower" 
INFO[0012] Networking is handled by "docker-bridge"     
INFO[0012] Started Firecracker VM "84dcb6201bca1467" in a container with ID "44f2b6e807c05933d544dbc900710d7985b4b76548753b197b8900be7a97ddf2" 
chanwit@chanwit-3558:~/.../projects/ignite
$ sudo bin/ignite ssh damp-flower
Welcome to Ubuntu 18.04.2 LTS (GNU/Linux 4.19.47 x86_64)
root@localhost:~# exit
logout
Connection to 172.17.0.2 closed.
$ docker ps
CONTAINER ID        IMAGE                                       COMMAND                  CREATED             STATUS              PORTS               NAMES
44f2b6e807c0        weaveworks/ignite:v0.5.2-1-c659a34acc2a73   "/usr/local/bin/igni…"   41 seconds ago      Up 38 seconds                           ignite-84dcb6201bca1467
chanwit@chanwit-3558:~/.../projects/ignite
$ sudo bin/ignite rm -f  damp-flower
INFO[0003] Removed VM with name "damp-flower" and ID "84dcb6201bca1467"