drivers: copy device config from live to target

Copy the device config from the live system to the target system.
This allows for modifying the device config in the early_commands
stage and having those changes persist during the install on the live
system.

subiquity/server/ubuntu_drivers.py

@@ -22,7 +22,7 @@
 
 from subiquity.server.curtin import run_curtin_command
 from subiquity.system_scripts.umockdev import configs, umockdev_wrapper
-from subiquitycore.file_util import write_file
+from subiquitycore.file_util import copy_file_if_exists, write_file
 from subiquitycore.utils import arun_command, orig_environ
 
 log = logging.getLogger("subiquity.server.ubuntu_drivers")
@@ -242,10 +242,10 @@ async def install_drivers(self, root_dir: str, context) -> None:
             self.wrapper_script_source,
             mode=0o777,
         )
-        write_file(
+        # copy from live system to copy any changes
+        copy_file_if_exists(
+            self.dev_config_path,
             f"{root_dir}/{self.dev_config_path}",
-            self.dev_config,
-            mode=0o777,
         )
         # Install wrapper script pre-reqs on target
         await run_curtin_command(