The existing code had the following serious problems:
* when trying to update EF.SST or EF.IST, it would write to EF.UST !
* shell commands were called ust_* even for the EST/IST files
Let's introduce the proper separation between what is shared and what
is file-specific.
Change-Id: Ie55669ca37a4762fac9f71b1db528ca67056e8dd