Fix `opam-licenses.sh` script
Fix `opam-licenses.sh` script

The script needs to write the extracted LICENSE(s) into a file
LICENSE.<package>.extracted. Note there can be more than one license
in the package.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@docker.com>

djs55/vpnkit,djs55/vpnkit,djs55/vpnkit