Ensure that libRSDriver gets child's exit signal

b/19934827

ProcessManager in libcore can reap unclaimed SIGCHLDs in its process
group.  To ensure that the exit signal is not caught by ProcessManager
and instead sent to libRS, set the child's PGID to its PID.

Change-Id: Ife548254c089ad50442ae202671e87e1846cba8c
1 file changed