arti: Add a keymgr feature.
Adding a keymgr feature here will enable us to detect if arti is
running without keymgr support. This is needed for the correct handling
of subcommands that require keymgr support (such as the arti hsc
subcommand).
Adding a keymgr feature here will enable us to detect if arti is
running without keymgr support. This is needed for the correct handling
of subcommands that require keymgr support (such as the arti hsc
subcommand).