Add command initialisation on record creation

This clears the invalid alarm status that the records would otherwise
have until processed the first time.

src/fastcs/backends/epics/ioc.py

@@ -80,7 +80,7 @@ def _create_and_link_command_pv(pv_name: str, method: Callable) -> None:
     async def wrapped_method(_: Any):
         await method()
 
-    builder.aOut(pv_name, always_update=True, on_update=wrapped_method)
+    builder.aOut(pv_name, initial_value=0, always_update=True, on_update=wrapped_method)
 
 
 def _create_and_link_attribute_pvs(mapping: Mapping) -> None: