[X/B/D][SRU] Fix for CVE-2019-20096

[Connor Kuehl]

https://people.canonical.com/~ubuntu-security/cve/2019/CVE-2019-20096.html

>From the link above:

    "In the Linux kernel before 5.1, there is a memory leak in
    __feat_register_sp() in net/dccp/feat.c, which may cause denial of service,
    aka CID-1d3ff0950e2b."

Clean cherry picks.