title: docker-compose does not initalize container environment variables
body: <p>I am trying to execute simple code.</p>
  
  <p>docker-compose.yml</p>
  
  <pre><code>version: '3.7'
  
  services:
    test-environment:
      image: alpine:3.9
      environment: 
        VAR1: 'variable 1'
        VAR2: '222'
      command: echo variable1 = $VAR1; variable2 = $VAR2
  </code></pre>
  
  <p>Expected behavior: to see in output </p>
  
  <pre><code>variable1 = variable 1; variable2 = 222
  </code></pre>
  
  <p>But after</p>
  
  <pre><code>docker-compose up
  </code></pre>
  
  <p>i got next:</p>
  
  <pre><code>WARNING: The VAR1 variable is not set. Defaulting to a blank string.
  WARNING: The VAR2 variable is not set. Defaulting to a blank string.
  Recreating project_test-environment_1 ... done
  Attaching to project_test-environment_1
  test-environment_1  | variable1 = ; variable2 =
  project_test-environment_1 exited with code 0
  </code></pre>
  
  <p>It seems like environment variables were not initialized. Using alternative syntax</p>
  
  <pre><code>environment:
   - VAR1='variable 1'
   - VAR2=222
  </code></pre>
  
  <p>given the same result too.</p>
  
  <p>docker info output:</p>
  
  <pre><code>Containers: 3
  Running: 0
  Paused: 0
  Stopped: 3
  Images: 5
  Server Version: 18.09.2
  Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
  Logging Driver: json-file
  Cgroup Driver: cgroupfs
  Plugins:
   Volume: local
   Network: bridge host macvlan null overlay
   Log: awslogs fluentd gcplogs gelf journald json-file local logentries 
   splunk syslog
  Swarm: inactive
  Runtimes: runc
  Default Runtime: runc
  Init Binary: docker-init
  containerd version: 9754871865f7fe2f4e74d43e2fc7ccd237edcbce
  runc version: 09c8266bf2fcf9519a651b04ae54c967b9ab86ec
  init version: fec3683
  Security Options:
   seccomp
   Profile: default
  Kernel Version: 4.9.125-linuxkit
  Operating System: Docker for Windows
  OSType: linux
  Architecture: x86_64
  CPUs: 1
  Total Memory: 973.8MiB
  Name: linuxkit-00155d694b07
  ID: NA32:YPM3:D5GL:JQBM:H4BN:LE2B:4HLN:5B4A:AI7T:6SDS:LSVZ:P74L
  Docker Root Dir: /var/lib/docker
  Debug Mode (client): false
  Debug Mode (server): true
   File Descriptors: 22
   Goroutines: 47
   System Time: 2019-05-14T08:44:02.5767035Z
   EventsListeners: 1
  Registry: https://index.docker.io/v1/
  Labels:
  Experimental: false
  Insecure Registries:
   127.0.0.0/8
  Live Restore Enabled: false
  Product License: Community Engine
  </code></pre>
  
  <p>Does anyone has any ideas to solve problem?</p>
  
  <p>P.S. Sorry for my English.</p>