lmkd: use libprocessgroup to kill forked processes

After sending sigkill to the main process, also call into
libprocessgroup to kill any processes that were forked.

Bug: 15313911
Change-Id: I05577c6f5b70800ce0a01f480c8870c2c601afda
diff --git a/lmkd.c b/lmkd.c
index 369b5ad..1aeb182 100644
--- a/lmkd.c
+++ b/lmkd.c
@@ -32,6 +32,7 @@
 
 #include <cutils/sockets.h>
 #include <log/log.h>
+#include <processgroup/processgroup.h>
 
 #ifndef __unused
 #define __unused __attribute__((__unused__))
@@ -591,6 +592,7 @@
                   other_file * page_k, minfree * page_k, min_score_adj,
                   other_free * page_k, other_free >= 0 ? "above" : "below");
             r = kill(pid, SIGKILL);
+            killProcessGroup(uid, pid, SIGKILL);
             pid_remove(pid);
 
             if (r) {