make azure pipelines upload coverage reports (nilearn#2419)

Problems and fixes:
--------------------------

- token was not shared with builds of forks (it's a box to tick
  somewhere in the web UI)
- the secret variable was not mapped as an environment variable (they
  are not decrypted unless you request it in the yaml file)
- the cmd script was using bash syntax to refer to the environment
  variable

Commits:
-------------

* update azure.yml

* iter

* iter

* iter

* iter

* iter

* iter

* remove verbose

* undo temp change

* clear circle ci cache

.circleci/docs-cache-timestamp

@@ -1 +1 @@
-2019-11-07 13:17:41.900352
+2020-04-28 23:03:23.904075

.circleci/packages-cache-timestamp

@@ -1 +1 @@
-2019-11-07 13:17:41.900617
+2020-04-28 23:03:23.904248

azure-pipelines.yml

@@ -38,8 +38,11 @@ jobs:
     displayName: 'test'
 
   - script: |
-      codecov -f coverage.xml --token=$(CODECOV_TOKEN)
+      codecov -f coverage.xml -t %CODECOV_TOKEN%
     displayName: 'codecov'
+    env:
+      CODECOV_TOKEN: $(CODECOV_TOKEN)
+
   - task: PublishTestResults@2
     inputs:
       testResultsFiles: '**/test-results.xml'