Update comments on now-unsed user ID and app ID tags.

I'd just remove them but Trusty keymaster has been generating keys with
KM_TAG_ALL_USERS and KM_TAG_ALL_APPLICATIONS, so removing them without
breaking those keys is tricky.  Plus I think they may come back.

Bug: 21845167
Change-Id: I3b807e3e4bee64eba72b7fa6f1ee1929c4ca9dd0
1 file changed