[ Merge of http://go/wvgerrit/174572 ]
Pass the real oemcrypto session id from `pair.session` instead of
`session` for CopyBuffer, since `session` can be changed when L1
and L3 are running in parallel and `session` in that case may not
be the correct oemcrypto session id any more.
Bug: 279967915
Test: wvts
Change-Id: Ic5e21ccb227d4c4992ef500435fa3b68812c4d9b