fix: handle undefined certname in convert_compiler_to_legacy plan

- Updated `primary_host` to handle cases where `certname` is undefined.
- Added conditional logic to default to `$primary_target` if `certname` is undefined.

Author: CoMfUcIoS

Diff for: plans/convert_compiler_to_legacy.pp

@@ -100,11 +100,17 @@
 
   apply($primary_target) {
     class { 'peadm::setup::node_manager_yaml':
-      primary_host => $primary_target.peadm::certname(),
+      primary_host => $primary_target.peadm::certname() ? {
+        undef   => $primary_target,
+        default => $primary_target.peadm::certname(),
+      },
     }
 
     class { 'peadm::setup::legacy_compiler_group':
-      primary_host                     => $primary_target.peadm::certname(),
+      primary_host                     => $primary_target.peadm::certname() ? {
+        undef   => $primary_target,
+        default => $primary_target.peadm::certname(),
+      },
       internal_compiler_a_pool_address => $cluster['params']['internal_compiler_a_pool_address'],
       internal_compiler_b_pool_address => $cluster['params']['internal_compiler_b_pool_address'],
       require                          => Class['peadm::setup::node_manager_yaml'],