Restore CMD rather than ENTRYPOINT (#136)

Switching to ENTRYPOINT broke the SO fixturenet stack.

I think there are arguments both ways as to whether ENTRYPOINT or CMD is more appropriate in this case, but in general I lean towards not breaking something that was working without a strong reason.

Reviewed-on: https://git.vdb.to/cerc-io/laconicd/pulls/136
Co-authored-by: Thomas E Lackey <telackey@bozemanpass.com>
Co-committed-by: Thomas E Lackey <telackey@bozemanpass.com>

Dockerfile

@@ -27,4 +27,4 @@ COPY --from=build-env /go/src/github.com/cerc-io/laconicd/build/laconicd /usr/bi
 
 WORKDIR /
 # Run laconicd by default
-ENTRYPOINT ["laconicd"]
+CMD ["laconicd"]