Fix crash importing from a directory special remote that contains a broken
symlink.
The crash was in listImportableContentsM but some other places in
Remote.Directory also seemed like they could have the same problem.
Also audited for other places that have such a problem. Not all calls
to getFileStatus are bad, in some cases it's better to crash on something
unexpected. For example, `git-annex import path` when the path is a broken
symlink should crash, the same as when it does not exist. Many of the
getFileStatus calls are like that, particularly when they involve
.git/annex/objects which should never have a broken symlink in it.
Fixed a few other possible cases of the problem.
Sponsored-by: Lawrence Brogan on Patreon
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