Make cmix package compile

cmix/address/addressSpace_test.go

cmix/identity/receptionID/identity_test.go

cmix/identity/receptionID/registration_test.go

cmix/identity/receptionID/store/checkedRounds_test.go

cmix/identity/receptionID/store/unknownRounds_test.go

cmix/identity/receptionID/store_test.go

cmix/identity/tracker_test.go

cmix/message/fingerprints_test.go

cmix/message/inProgress_test.go

cmix/message/meteredCmixMessageBuffer_test.go

cmix/pickup/store/uncheckedRounds_test.go