[CHORE] flake8 issues E402, E721 and F821 (#1874)

* F821: undefine name
disabled and logged webhook_listener for opennode and lnpay because they are obviously not working
* E402: module level import not at top of file
* E721 fixes, only popped up for python3.9 not 3.10

lnbits/server.py

@@ -1,17 +1,16 @@
-import uvloop
-from uvicorn.supervisors import ChangeReload
-
-uvloop.install()
-
 import multiprocessing as mp
 import time
 from pathlib import Path
 
 import click
 import uvicorn
+import uvloop
+from uvicorn.supervisors import ChangeReload
 
 from lnbits.settings import set_cli_settings, settings
 
+uvloop.install()
+
 
 @click.command(
     context_settings=dict(