This is a follow-up of commit 8712c638
which fixed the following case:

  A  B  C  D    # transactions
  r  r
     A  r  r
        R1 R2
           A3

where A stands for Append, R for Rotate, and uppercase for conflict resolution

  A3 contained duplicated elements from both R1 & R2 (those added by B)

This commit fixes the same issue during rotation:

  A  B  C
  a  a
  A     r
     A  R
        R

  (elements added by A were duplicated)