Camera: fix release fence logic

According to spec, HAL will set release_fence to acquire_fence
when error happened (usually during flush call). Camera service
should not refer to the acquireFence anyhow since per spec HAL
needs to set it to -1 if acquireFence has been waited on.

Change-Id: I809355d0c8c71f78f657e37d19221fd1f5bdc90b