Camera: Avoid freeing outstanding input buffers

The producer end can disconnect at any time which
will trigger the freeing of the input buffer. If
any input buffers are outstanding and being processed
by the camera device freeing them can cause stability
issues.

Bug: 63682712
Test: Manual using application.
Change-Id: I25da97786d75e82b1b13dce34953de597bea9b2e