There are multiple ways how states can be processed during tests. One is
through tests/mocking, the other through tests/xxxutil. Both methods can
create genesis states with a set of deposits from mock validators. The
private keys for those validators are created differently, though. While
tests/mocking generates random keys, testblockutil generates fixed keys.
This is a problem when mixing both tests/mocking and testblockutil in a
single test case, as they assume that the deposits were generated using
the same method. This patch aligns the key generation across tests.