Make `import Server` in `nut.py` conditional

[ii0606226]

Move import Server into if args.server: code block so it doesn't get imported when it's not used (i.e. on python nut.py --decompress <filename>) and doesn't throw an exception on pycurl-less systems (i.e. Windows as per requirements.txt, line 20). Minimal testing done: before change --decompress throws an exception; after change --decompress works, -S throws an exception.

[bd82aa5c1aaecdb2559d]

for pycurl on windows use the prebuilt wheel - https://github.com/blawar/nut/blob/master/tests/pycurl-7.43.0.5-cp39-cp39-win_amd64.whl