Remove symbolic link in Dockerfile

[vnghia]

This line

i2pd/contrib/docker/entrypoint.sh

Line 9 in 69ee611

ln -s /i2pd_certificates "$DATA_DIR"/certificates

is causing me trouble when I try to bind mount /home/i2pd/data/ with a named volume. My suggestion is we remove this line and add a --certsdir to $DEFAULT_ARGS which will point to /i2pd_certificates.

I can send a PR for this.

Furthermore, if I want to keep the data in the docker file persistent, I got this error after restart the container (without removing the bind volume): ln: /home/i2pd/data/certificates/i2pd_certificates: File exists