Deal with non-strings in is_uuid?

In d971ad5 the method was rewritten
with the intention of being compatible with Ruby 3.3 where =~ is only
defined on strings.

A problem with this is that /regex/.match?(nil) works, but
/regex/.match?(42) raises a TypeError. It would have been broken with
the old code on Ruby 3.3 as well, but only raised a deprecation warning
on prior versions.

Fixes: d971ad5 ("Fix warning on nil comparison")

Author: ekohl

lib/fog/vsphere/compute.rb

@@ -347,7 +347,7 @@ def managed_obj_id(obj)
         end
 
         def is_uuid?(id)
-          /[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}/.match?(id)
+          id.is_a?(String) && /[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}/.match?(id)
         end
       end