dir/dircache: fix logging
dir/dircache: fix logging

Change-Id: I2b069e35c297b77d5e97f1c4f8dc0b455fb52ffe
Reviewed-on: https://upspin-review.googlesource.com/8275
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

upspin/upspin,upspin/upspin