Merge pull request #2182 in SNORT/snort3 from ~STECHEW/snort3:retry_in_appid to master

Merge pull request #2182 in SNORT/snort3 from ~STECHEW/snort3:retry_in_appid to master

Squashed commit of the following:

commit 2051a456ec98881eb3f9c4bf72c8d208700e804e
Author: Steve Chew <stechew@cisco.com>
Date:   Wed Apr 29 23:19:24 2020 -0400

    appid: Make unit tests multithread safe.

commit b11c6c8c20b671e2645adbf9c1ac779223927e97
Author: Steve Chew <stechew@cisco.com>
Date:   Fri Apr 24 18:35:12 2020 -0400

    appid: On API call store new values and publish an event for them immediately.

commit 5d5fdc18224e6e0b927080ebdf9c8761139b9e20
Author: Steve Chew <stechew@cisco.com>
Date:   Wed Apr 22 17:10:15 2020 -0400

    appid: Do not process retry packets but continue processing future packets in AppId.