set /proc/sys/net/unix/max_dgram_qlen to large value

- init: set /proc/sys/net/unix/max_dgram_qlen to 300
- libsysutils: Add listen backlog argument to startListener
- logd: set listen backlog to 300

Change-Id: Id6d37d6c937ba2d221e76258d89c9516619caeec
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 9975368..ffbc9fa 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -100,6 +100,7 @@
     write /proc/sys/kernel/dmesg_restrict 1
     write /proc/sys/vm/mmap_min_addr 32768
     write /proc/sys/net/ipv4/ping_group_range "0 2147483647"
+    write /proc/sys/net/unix/max_dgram_qlen 300
     write /proc/sys/kernel/sched_rt_runtime_us 950000
     write /proc/sys/kernel/sched_rt_period_us 1000000