fix(operations/crontab): only provide command if cron_name is not provided

Author: information-redacted

pyinfra/operations/crontab.py

@@ -84,7 +84,7 @@ def comma_sep(value):
         ctb = ctb0
     name_comment = "# pyinfra-name={0}".format(cron_name)
 
-    existing_crontab = ctb.get_command(command=command, name=cron_name)
+    existing_crontab = ctb.get_command(command=[command if cron_name is None else None], name=cron_name)
     existing_crontab_command = existing_crontab["command"] if existing_crontab else command
     existing_crontab_match = existing_crontab["command"] if existing_crontab else command