Extract Advisory.Description on RHEL, Amazon, Oracle

[kotakanbe]

Extract the description of yum --color=never --security updateinfo updates, and put it into JSON.

===============================================================================
  Amazon Linux AMI 2014.03 - ALAS-2016-720: medium priority package update for wget
===============================================================================
  Update ID : ALAS-2016-720
    Release :
       Type : security
     Status : final
     Issued : 2016-07-14 16:30
       CVEs : CVE-2016-4971
Description : Package updates are available for Amazon Linux AMI that fix the
            : following vulnerabilities: CVE-2016-4971:
            :         GNU wget before 1.18 allows remote servers
            :         to write to arbitrary files by redirecting
            :         a request from HTTP to a crafted FTP
            :         resource. 1343666:
            : CVE-2016-4971 wget: Lack of filename checking
            : allows arbitrary file upload via FTP redirect
   Severity : medium