Pass a valid fence time if the acquire fence has not signaled

When we try to latch a buffer with an unsignaled fence, we were passing
Fence::SIGNAL_TIME_PENDING (MAX_INT) as the acquire fence time,
marking all the app frametimeline as missed. This is a short term solution
to provide a reasonable value instead.

Flag: EXEMPT bugfix
Fixes: 344175037
Test: cb test + perfetto
Change-Id: Ia226589c177457f28540b040086903e518796436