[ci] Pin specific CI tests to Debian Buster

Some roles don't work on Debian Bullseye, either due to missing
packages, APT repositories not available yet or other external factors.
For now, these roles will be ested using Debian Buster which should work
as expected.

(cherry picked from commit 5823553)
(cherry picked from commit 5c43798)

.gitlab-ci.yml

@@ -348,6 +348,8 @@ stages:
     - 'apt_preferences role'
     - 'java role'
   variables:
+    # The cran packages are not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'cran.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/cran.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_cran'
@@ -575,6 +577,8 @@ stages:
     - 'keyring role'
     - 'apt_preferences role'
   variables:
+    # The elastic repository is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'elastic_co.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/elastic_co.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_elastic_co'
@@ -593,6 +597,8 @@ stages:
     - 'java role'
     - 'elastic_co role'
   variables:
+    # The elastic repository is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'elasticsearch.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/elasticsearch.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_elasticsearch'
@@ -760,6 +766,8 @@ stages:
     - 'apt_preferences role'
     - 'elastic_co role'
   variables:
+    # The elastic repository is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'filebeat.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/filebeat.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_filebeat'
@@ -813,6 +821,8 @@ stages:
   needs:
     - 'keyring role'
   variables:
+    # The gitlab-runner package is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'gitlab_runner.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/gitlab_runner.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_gitlab_runner'
@@ -830,6 +840,8 @@ stages:
     - 'docker_server role'
     - 'gitlab_runner role'
   variables:
+    # The gitlab-runner package is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'gitlab_runner.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/docker_server.yml ${DEBOPS_PLAYBOOKS}/service/gitlab_runner.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_docker_server,debops_service_gitlab_runner'
@@ -844,6 +856,8 @@ stages:
     - 'python role'
     - 'libvirt role'
   variables:
+    # The gitlab-runner package is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'gitlab_runner.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/libvirtd.yml ${DEBOPS_PLAYBOOKS}/service/gitlab_runner.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_libvirtd,debops_service_gitlab_runner'
@@ -863,6 +877,8 @@ stages:
     - 'lxc role'
     - 'keyring role'
   variables:
+    # The gitlab-runner package is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'gitlab_runner.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/lxc.yml ${DEBOPS_PLAYBOOKS}/service/gitlab_runner.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_lxc,debops_service_gitlab_runner'
@@ -1133,6 +1149,8 @@ stages:
     - 'nginx role'
     - 'elastic_co role'
   variables:
+    # The elastic repository is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'kibana.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/kibana.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_kibana'
@@ -2141,6 +2159,8 @@ stages:
 'rsnapshot role':
   <<: *test_role_no_deps
   variables:
+    # The rsnapshot package is not available in Bullseye
+    BASE_VAGRANT_BOX: 'debian/buster64'
     JANE_TEST_FACT: 'rsnapshot.fact'
     JANE_TEST_PLAY: '${DEBOPS_PLAYBOOKS}/service/rsnapshot.yml'
     JANE_INVENTORY_GROUPS: 'debops_service_rsnapshot'