Do not run apt update in dry-run mode

update requires root access to the machine and there is no --simulate
option so skip it in dry-run mode.

Co-authored-by: Didier Roche <didrocks@ubuntu.com>

system_setup/server/controllers/configure.py

@@ -186,6 +186,7 @@ class ConfigureController(SubiquityController):
             log.error('Failed to detect recommended language packs.')
             return False
 
+        if not self.app.opts.dry_run:
             cp = await arun_command([aptCommand, "update"], env=env)
             if cp.returncode != 0:
                 log.debug("Failed to update apt cache.\n%s", cp.stderr)