This usually occurs when re-initializing a file credential
cache over the top of an existing one.
This was meant to be fixed in commit 48cb3aa by calling
fcc_destroy(), but that only unlinks the "from" file
(which was already renamed or unlinked) but still doesn't
free the in-memory credentials. Using fcc_close() instead of
fcc_destroy() frees the leaked in-memory credentials.
Signed-off-by: Love Hornquist Astrand <lha@h5l.org>