Don't try to cleanup symlinked jobs

[albertz]

We started to share more common job dirs. In my case, they are symlinked.

[2023-11-19 18:36:36,651] INFO: clean up: work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.OjEfOC2QXh8l                        
[2023-11-19 18:36:36,652] WARNING: Could not clean up work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.wjSkfzJS1Ge2: [Errno 13] Permission denied: '/u/zeyer/setups/combined/2021-05-31/work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.wjSkfzJS1Ge2/work'   
[2023-11-19 18:36:36,653] WARNING: Could not clean up work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.N4devEBOAvgK: [Errno 13] Permission denied: '/u/zeyer/setups/combined/2021-05-31/work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.N4devEBOAvgK/work'   
[2023-11-19 18:36:36,655] WARNING: Could not clean up work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.h78m0D0Rx6uQ: [Errno 13] Permission denied: '/u/zeyer/setups/combined/2021-05-31/work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.h78m0D0Rx6uQ/work'   
[2023-11-19 18:36:36,662] WARNING: Could not clean up work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.OjEfOC2QXh8l: [Errno 13] Permission denied: '/u/zeyer/setups/combined/2021-05-31/work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.OjEfOC2QXh8l/work'   
[2023-11-19 18:36:36,662] WARNING: Could not clean up work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.2GMuOxuirZVL: [Errno 13] Permission denied: '/u/zeyer/setups/combined/2021-05-31/work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.2GMuOxuirZVL/work'   

With symlinks for example like:
work/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.OjEfOC2QXh8l -> /work/common/asr/librispeech/data/sisyphus_work_dir/i6_core/datasets/librispeech/LibriSpeechCreateBlissCorpusJob.OjEfOC2QXh8l

My suggestion is to never clean up job dirs which are symlinks. E.g. we could add such a check in Job._sis_cleanable.

Do you agree? Or other suggestions? Should this be an option or just the new behavior? If this is supposed to be an option, what should be its default?

[albertz]

Ah, I just see that #105 is a duplicate of this.