fix: no longer print invalid api cert

- previously, if routing-api was disabled, we would return
a ruby object in the cert files for route-registrar
- fixes #155

[#168138145]

Co-authored-by: Tim Downey <[email protected]>

Author: angelachin

jobs/route_registrar/templates/client.crt.erb

@@ -7,6 +7,8 @@
         return link.p('routing_api.mtls_client_cert')
       end
     end
+
+    return ''
   end
 
   client_cert

jobs/route_registrar/templates/client_private.key.erb

@@ -7,6 +7,8 @@
         return link.p('routing_api.mtls_client_key')
       end
     end
+
+    return ''
   end
 
   client_private_key

jobs/route_registrar/templates/server_ca.crt.erb

@@ -7,6 +7,8 @@
         return link.p('routing_api.mtls_ca')
       end
     end
+
+    return ''
   end
 
   server_ca_cert