evolve: don't make values of replacements dict lists
There was inconsistency in code base related to the values stored in
replacements dict in evolvestate. At some places we store a list, at some places
we just store the nodeid. Let's make sure we store only the nodeid, not a list.
If there are cases, when there are multiple replacements or changesets created
during resolution, later patch will introduce storing temprevs in evolvestate
which should be used.