Merge pull request #710 in SNORT/snort3 from more_misc_fixes to master

Merge pull request #710 in SNORT/snort3 from more_misc_fixes to master

Squashed commit of the following:

commit a0941af98b9d31cbed6dde9eb1cad27404ce76d4
Author: Russ Combs <rucombs@cisco.com>
Date:   Fri Nov 18 13:21:57 2016 -0500

    fix race with multiple packet threads

commit 53d440735a497d58a5ae7c7bbdd9f7443d61d158
Author: Russ Combs <rucombs@cisco.com>
Date:   Fri Nov 18 08:10:21 2016 -0500

    create pid file after dropping privs

commit f4e784f86cd395ef70710eec17c32726d7047b62
Author: Russ Combs <rucombs@cisco.com>
Date:   Fri Nov 18 08:08:19 2016 -0500

    proper cleanup of port objects in failure cases

commit a6b45aa3d2ddc6ca5de9d1df8fde5148f8b2fdd6
Author: Russ Combs <rucombs@cisco.com>
Date:   Fri Nov 18 07:14:05 2016 -0500

    only print file stats banner if stats available