Installation checker about marfs

[jti-lanl]

TBD:

• Regarding namespace permissions, marfs_config should print them out as a list of strings, rather than just show the bit-mask.

• marfs_config should show the "generic" per-DAL config options. I think those must've been introduced after marfs_config.

• Currently, path-expansion happens in two phases. After the first phase (mc_update_path on the template from the config), all that needs substituting-in during the second phase is the block-number. This could be done programmatically, by looking at the MC DAL config options (see previous item). One could then generate all the per-block paths.

  After we pivot to RDMA code, the path-template expansion (for RDMA and for MC) is done by a per-DAL snprintf function. Formerly, this snprintf was internal to libne functions. I'm not saying we must go straight to this for Brett's issue, but filling out the template in the case of RDMA paths is a little more complex, and more-likely requires access to the per-DAL config options.

  When we get to RDMA repos, there is also test_client which allows you to interact with server(s) on each individual storage node, using a generic path-template. If you know the name of an object-file on a given server, you can use the "template" file on the command line. It supports a stat function, but we could add something else, if needed.