Testing build matrix

Changes azure-pipelines to have 3 different stages: fedora-latest,
centos-7 and centos-8.

tests/azure/azure-pipelines.yml

@@ -17,8 +17,10 @@ trigger:
 pool:
   vmImage: 'ubuntu-18.04'
 
-jobs:
+stages:
-- job: RunLinters
+- stage: Linters
+  jobs:
+  - job: RunLinters
     displayName: Run Linters
     steps:
     - task: UsePythonVersion@0
@@ -37,20 +39,26 @@ jobs:
     - script: pydocstyle .
       displayName: Verify docstings
 
-- template: templates/playbook_tests.yml
+- stage: Centos7
+  dependsOn: []
+  jobs:
+  - template: templates/group_tests.yml
     parameters:
-    group_number: 1
-    number_of_groups: 3
       build_number: $(Build.BuildNumber)
+      scenario: centos-7
 
-- template: templates/playbook_tests.yml
+- stage: Centos8
+  dependsOn: []
+  jobs:
+  - template: templates/group_tests.yml
     parameters:
-    group_number: 2
-    number_of_groups: 3
       build_number: $(Build.BuildNumber)
+      scenario: centos-8
 
-- template: templates/playbook_tests.yml
+- stage: FedoraLatest
+  dependsOn: []
+  jobs:
+  - template: templates/group_tests.yml
     parameters:
-    group_number: 3
-    number_of_groups: 3
       build_number: $(Build.BuildNumber)
+      scenario: fedora-latest

tests/azure/build-containers.yml

@@ -6,6 +6,9 @@ schedules:
   branches:
     include:
     - master
+  always: true
+
+trigger: none
 
 pool:
   vmImage: 'ubuntu-18.04'

tests/azure/templates/group_tests.yml

@@ -0,0 +1,29 @@
+
+parameters:
+  - name: scenario
+    type: string
+    default: centos-8
+  - name: build_number
+    type: string
+
+jobs:
+- template: playbook_tests.yml
+  parameters:
+    group_number: 1
+    number_of_groups: 3
+    build_number: ${{ parameters.build_number }}
+    scenario: ${{ parameters.scenario }}
+
+- template: playbook_tests.yml
+  parameters:
+    group_number: 2
+    number_of_groups: 3
+    build_number: ${{ parameters.build_number }}
+    scenario: ${{ parameters.scenario }}
+
+- template: playbook_tests.yml
+  parameters:
+    group_number: 3
+    number_of_groups: 3
+    build_number: ${{ parameters.build_number }}
+    scenario: ${{ parameters.scenario }}

tests/azure/templates/playbook_tests.yml

@@ -16,10 +16,12 @@ parameters:
     type: string
     default: 3.6
   - name: build_number
+    type: string
+
 
 jobs:
-- job: RunTests${{ parameters.group_number }}
+- job: Test_Group${{ parameters.group_number }}
-  displayName: Run tests ${{ parameters.group_number }}/${{ parameters.number_of_groups }}
+  displayName: Run tests ${{ parameters.scenario }} (${{ parameters.group_number }}/${{ parameters.number_of_groups }})
   steps:
   - task: UsePythonVersion@0
     inputs: