Add connection service focus api to the fake CS

This added a default implementation of connection service focus api to
the fake ConnectionService to avoid the compiled error.

Bug: 69651192
Test: manual

Change-Id: I01ecc7f6a89f0d3794edd51f939a85d9a113a703
Merged-In: I01ecc7f6a89f0d3794edd51f939a85d9a113a703