Update rpi-sb-keywriter.service

Move the instance specifier to the correct location.

Author: tdewey-rpi

key-writer/rpi-sb-keywriter.service

@@ -5,4 +5,4 @@ Description=Provision signing keys to a Raspberry Pi Device
 Type=oneshot
 ExecStart=/usr/local/bin/keywriter.sh %I
 EnvironmentFile=/etc/rpi-sb-provisioner/config
-StandardOutput = file:/var/log/rpi-sb-provisioner/%I/keywriter.log
+StandardOutput=file:/var/log/rpi-sb-provisioner/keywriter/%I.log