inventory: Exclude test machines by default

We don't want Jenkins attemptying to manage test VMs.  I thought of
various ways to exclude them, but in the end, I think a simple name
match will work fine.

The host provisioner _should_ manage test VMs, though, so it will need
to be configured to set the `PYROCUFFLINK_EXCLUDE_TEST` environment
variable to `false` to override the default behavior.

plugins/inventory/pyrocufflink.py

@@ -44,6 +44,12 @@ options:
     description: Exclude domains running specified operating systems
     type: list
     default: []
+  exclude_test:
+    description: Exclude domains whose name implies they are testing machines
+    type: boolean
+    default: true
+    env:
+    - name: PYROCUFFLINK_EXCLUDE_TEST
   log_excluded:
     description:
       Print a log message about excluded domains, useful for troubleshooting
@@ -90,6 +96,7 @@ class InventoryModule(BaseInventoryPlugin, Constructable):
         dns_domain = self.get_option('dns_domain')
         exclude_off = cast(bool, self.get_option('exclude_off'))
         exclude_os = cast(list[str], self.get_option('exclude_os'))
+        exclude_test = cast(list[str], self.get_option('exclude_test'))
         log_excluded = cast(bool, self.get_option('log_excluded'))
 
         assert self.inventory
@@ -117,6 +124,13 @@ class InventoryModule(BaseInventoryPlugin, Constructable):
                             host.os_id,
                         )
                     continue
+                if exclude_test and host.is_test_host:
+                    if log_excluded:
+                        log.warning(
+                            'Excluding libvirt domain %s (test machine)',
+                            host.name,
+                        )
+                        continue
                 if host.title:
                     inventory_hostname = host.title
                 else:
@@ -154,6 +168,10 @@ class Host:
     def groups(self) -> list[str]:
         return list(self._groups())
 
+    @functools.cached_property
+    def is_test_host(self) -> bool:
+        return self.name.startswith('test-')
+
     @functools.cached_property
     def libosinfo(self) -> Optional[etree.Element]:
         try: