[catnip] Append an empty string at eal_init args to be skipped

[ihchoi12]

Description

This PR solves #536

Summary of Changes

Just append an empty string to eal_init in the default.yaml configuration file.

[iyzhang]

Thanks for doing this! Can you do a git rebase against dev and squash your commits into one commit?

[ihchoi12]

Done. Thanks for the suggestion!

[carvalhof]

Another possibility is to insert a string (e.g., "") at the first position of eal_init_refs vector in the initialize_dpdk function. Branch bugfix-dpdk-eal presents this possibility.