Partially revert "Merge pull request #2679 from AZero13/error"

Partially revert "Merge pull request #2679 from AZero13/error"

This reverts commit d8aaf88c9feab047139df4cae60d845764a2480a, reversing
changes made to ee49ac81068f93754f004368f2cc72c95a8bf056.

tree_reopen() and tree_dup() return NULL only of they
are unable to allocate memory. Otherwise libarchive enters
ARCHIVE_FATAL if trying to walk an enterable but unreadable
directory.

__archive_ensure_cloexec_flag() operates only on fd >= 0
so there is no need to skip it

I have reimplemented the check around fdopendir()

Reported by:	Christian Weisgerber from OpenBSD