[FAB-1781] Fix failing test in multichain package

https://jira.hyperledger.org/browse/FAB-1781

Changesets [1] and [2] got merged and as a result a test in the
`multichain` package fails.

This changeset fixes the failing test.

[1] https://gerrit.hyperledger.org/r/3867
[2] https://gerrit.hyperledger.org/r/4581



Change-Id: I2dfc6403f79914943107a77b587791800ac053eb
Signed-off-by: Kostas Christidis <kostas@christidis.io>