distro/tests: use rocky8 instead of centos8

.gitlab-ci.yml

@@ -632,12 +632,11 @@ obs:build:all:
     when:
       - script_failure
 
-obs:centos8:x86_64:
+obs:rocky8:x86_64:
   <<: *distrotest
-  allow_failure: true
   variables:
     OBS_REPO: knot-resolver-latest
-    DISTROTEST_NAME: centos8
+    DISTROTEST_NAME: rocky8
     DISTROTEST_REPO: CentOS_8_EPEL
 
 obs:debian9:x86_64:

distro/tests/centos8/Vagrantfile → distro/tests/rocky8/Vagrantfile

@@ -5,10 +5,10 @@
 
 Vagrant.configure(2) do |config|
 
-    config.vm.box = "centos/8"
+    config.vm.box = "generic/rocky8"
     config.vm.synced_folder ".", "/vagrant", disabled: true
 
-    config.vm.define "centos8_knot-resolver"  do |machine|
+    config.vm.define "rocky8_knot-resolver"  do |machine|
         machine.vm.provision "ansible" do |ansible|
             ansible.playbook = "../knot-resolver-pkgtest.yaml"
             ansible.extra_vars = {