Fix EnvSort so that env variables are populated properly

[procrypt]

Environment variables in docker-compose file are populated in random order resulting in failure of the functional test in golang.

I have used multiple docker-compose files to test this out from
fixtures folder.
docker-compose file used 1 and 2

$ kompose convert --provider=openshift -f docker-k8s.yml -f docker-os.yml --stdout -j > a.json
$ kompose convert --provider=openshift -f docker-k8s.yml -f docker-os.yml --stdout -j > b.json

$ diff a.json b.json

126a127,130
>                     "name": "DB_DBID",
>                     "value": "openshift"
>                   },
>                   {
140,143d143
<                     "value": "openshift"
<                   },
<                   {
<                     "name": "DB_DBID",

Sorting this struct

type EnvVar struct {
	Name  string
	Value string
}

would fix this issue.
This issue is a blocker for #518

[procrypt]

I'm working on this.