It is fine to use MockVariableValue to change a setting such as:
defer test.MockVariableValue(&setting.Mirror.Enabled, true)()
But when testing for errors and mocking a function, multiple variants
of the functions will be used, not just one. MockProtect a function
will make sure that when the test fails it always restores a sane
version of the function. For instance:
defer test.MockProtect(&mirror_service.AddPushMirrorRemote)()
mirror_service.AddPushMirrorRemote = mockOne
do some tests that may fail
mirror_service.AddPushMirrorRemote = mockTwo
do more tests that may fail
(cherry picked from commit 884b3c0f4b)
