logd: increase dgram_max_qlen to 600

Seeing liblog messages on system_server runtime restart
(too much system_server spam, 566 messages in 72ms)

Bug: 23788621
Change-Id: I5171f2c19a3538da190fc6c2b40e978d89bf0e20
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 5f1169d..dc85d98 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -86,7 +86,7 @@
     write /proc/sys/kernel/kptr_restrict 2
     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/net/unix/max_dgram_qlen 600
     write /proc/sys/kernel/sched_rt_runtime_us 950000
     write /proc/sys/kernel/sched_rt_period_us 1000000