Replace 'unblock' channels in mocks with 'WaitUntil'

[stoewer]

Many mocks used for unit testing use a channel called unblock in order to delay method invocation:

type someMock struct {
	mock.Mock
	unblock chan struct{}
}

This kind of constructs could be replaces with functionality provided by the used mocking library, which has already a function called WaitUntil that does the exact same thing.

Therefore all existing uses of unblock channels can be replaced with more idiomatic code.

[krnkl]

Will take this issue