journal: avoid infinite recursion when closing bad journal FD

journal: avoid infinite recursion when closing bad journal FD

When trying to log, if we fail we try to close the journal FD. If
it is bad, safe_close() will fail and assert, which will try to log,
which will fail, which will try to close the journal FD...
Infinite recursion looks very pretty live in gdb, but let's avoid
that by immediately invalidating the journal FD before closing it.