Accept a command list in check_call

check_output unwraps a single list argument, check_call never did, so
callers passing a list hit a TypeError out of create_subprocess_exec.
Two callers do: the genisoimage run behind Windows profile imports,
where an except Exception swallows the failure and the boot.iso is
silently missing, and the nodeconfig run in discovery, which takes out
automatic node configuration on discovery outright.

confluent_server/confluent/util.py

@@ -52,6 +52,8 @@ def mkdirp(path, mode=0o777):
 
 
 async def check_call(*cmd, **kwargs):
+    if len(cmd) == 1 and isinstance(cmd[0], (list, tuple)):
+        cmd = cmd[0]
     subproc = await asyncio.create_subprocess_exec(*cmd, **kwargs)
     rc = await subproc.wait()
     if rc != 0: