Move topic to Injecting Data section. (#3622)

* Move topic to Injecting Data section.

* Move included file.

docs/tasks/inject-data-application/define-environment-variable-container.md

@@ -1,5 +1,8 @@
 ---
 title: Defining Environment Variables for a Container
+redirect_from:
+- "/docs/tasks/configure-pod-container/define-environment-variable-container/"
+- "/docs/tasks/configure-pod-container/define-environment-variable-container.html"
 ---
 
 {% capture overview %}
@@ -30,7 +33,7 @@ file for the Pod defines an environment variable with name `DEMO_GREETING` and
 value `"Hello from the environment"`. Here is the configuration file for the
 Pod:
 
-{% include code.html language="yaml" file="envars.yaml" ghlink="/docs/tasks/configure-pod-container/envars.yaml" %}
+{% include code.html language="yaml" file="envars.yaml" ghlink="/docs/tasks/inject-data-application/envars.yaml" %}
 
 1. Create a Pod based on the YAML configuration file: