Fix ekv.Memstore creation in e2e

e2e/manager_test.go

e2e/parse/conversation/partner_test.go

e2e/parse/conversation/ring_test.go

e2e/parse/conversation/store_test.go

e2e/parse/partition/multiPartMessage_test.go

e2e/parse/partition/part_test.go

e2e/parse/partition/store_test.go

e2e/parse/partition_test.go

e2e/ratchet/partner/relationship_test.go

e2e/ratchet/partner/utils_test.go

e2e/ratchet/ratchet_test.go

e2e/ratchet/utils_test.go

e2e/rekey/confirm_test.go

e2e/rekey/exchange_test.go

e2e/rekey/rekey_test.go

e2e/rekey/trigger_test.go