[#679] Rename 'mock' part of tests to say 'fake'

Problem: We have some tests in morley-client program that uses a mock that provides a mock tezos-client and network state. But this holds some state and implements some logic on the stored state. So there is some concern that these things should be called a "fake" instead of a "mock".

Solution: Change all references to "mock" to "fake" in the context of these tests.

resolves: #679 (closed)