libfuse: fix log call depth
libfuse: fix log call depth

Avoid the dreaded "standard.go" log message by using extra call depth,
and even more call depth in `reportErr`.

Issue: KBFS-535

keybase/client,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client