Change constructor of ServiceManagerShim

Without this change the defaultServiceManager()
would return a ServiceManagerShim with a BackendUnifiedServiceManager
holding a BackendUnifiedServiceManager.

Test: atest aidl_integration_test
Bug: 333854840
Flag: Exempt Bugfix
Change-Id: I3d3bcfa3392da89085b8f034c42aff30759a2cd2
1 file changed