Pair tarfile hard-link / symlink checks with the correct predicate

[Chessing234]

Bug

_check_tarinfo in openedx/core/lib/extract_archive.py reports the
wrong link type when it blocks an unsafe archive member: a malicious
symbolic link is logged and raised as a "Hard link", and a malicious
hard link is logged and raised as a "Symlink".

Root cause

if finfo.issym() and _is_bad_link(finfo, base):
    log.debug(\"File %r is blocked: Hard link to %r\", finfo.name, finfo.linkname)
    raise SuspiciousOperation(\"Hard link\")
if finfo.islnk() and _is_bad_link(finfo, base):
    log.debug(\"File %r is blocked: Symlink to %r\", finfo.name, finfo.linkname)
    raise SuspiciousOperation(\"Symlink\")

Per Python's tarfile module:

• TarInfo.issym() — Return True if it is a symbolic link.
• TarInfo.islnk() — Return True if it is a hard link.

So the predicate guarding each branch is the opposite of its label and
debug message. Both kinds of unsafe link are still blocked (because both
arms exist), but the error message and log line attribute the wrong
category — which is misleading for operators looking at the log and for
any downstream code keying off the SuspiciousOperation reason string.

Why the fix is correct

• finfo.islnk() is the authoritative hard-link predicate, so it
  belongs with the "Hard link" label and debug line.
• finfo.issym() is the symbolic-link predicate, so it belongs with
  the "Symlink" label and debug line.
• The fix only swaps the two predicates; both raise sites and the
  subsequent finfo.isdev() check are unchanged, and every unsafe link
  remains blocked.

Change

openedx/core/lib/extract_archive.py: swap finfo.issym() and
finfo.islnk() in _check_tarinfo so each predicate matches its
block label. Two-line change.

[openedx-webhooks]

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