MFH: r423677

net-mgmt/unifi5: Update to 5.2.9

Changelog: https://community.ubnt.com/t5/UniFi-Updates-Blog/UniFi-5-2-9-is-released/ba-p/1694199

MFH due to important bugfixes and encouragement to upgrade from unifi4 which is EoL 2017-01-01

Approved by: ports-secteam (with hat)