etcd-io/etcd#9073 did not actually do what was intended: it still reads the entire raft log even though it now only needs the last entry. The last index is known so the call to entries needs to be adjusted so we only load the data we need.

This change should be backported to release-2.0 because we intended for this problem to be fixed in 2.0, and it's showing up in #26830.