WL#4547: Split ha_rnd_init into ha_rnd_init and ha_rnd_scan_init()

Affects: Server-6.1   —   Status: Un-Assigned   —   Priority: Medium

ha_rnd_init() initializes the "random access" cursor.
ha_rnd_init(1) initializes the "scan" cursor.
These are separate cursor types.
There should be separate calls to create and destroy them.