Camera: make fence import agnostic to hidl transport

This will introduce one more FD dup/close in passthrough mode, but
we have no other choice as camera server will not know whether
it is running in passthrough or binderized mode.

Test: running Camera2 API CTS
Bug: 30985004
Change-Id: I407d54a51c51fc09477dfb6236ab1b53bb1e0a21