This is to allow passing the elliptics node list through a string (so an env var can be used). Previously `elliptics_nodes` only accepted a hash/dictionary. This change makes it so that it also accepts a list/array or a string.
For example:

    elliptics:
      elliptics_nodes:
        - 1.1.1.1:2222
        - 1.1.1.2:2222

or

    elliptics:
      elliptics_nodes: "1.1.1.1:2222 1.1.1.2:2222"