When vi-mode is enabled, the mode prompt is too, but the cursor function isn't. We should expose the feature by default.
There's also the issue that it doesn't set default cursor shapes, so even if it were called by default it wouldn't do anything. It should probably default to "line" for insert mode and "block" for default/normal mode.
fish version installed: fish, version 2.3.1-363-g733e960
OS/terminal used: Archlinux, Konsole
Fish should change the cursor.
(Related to #1403 (comment))
Use fish_vi_cursor by default