Description of problem:
In the updateinfo.xml.gz files the href entry for bugs in an erratum will be empty if the erratum doesn't have a url stored in the db. The correct behavior is for us to generate a bugzilla url based on the bug id.

Example:
Old (broken) xml:
<update from="" status="final" type="bugfix" version="1"><id>CL-BA-2013:0408</id><title>cifs-utils bug fix and enhancement update</title>...<references><reference href="" id="838606" type="bugzilla">enable PIE and RELRO in cifs-utils binaries</reference></references>...</update>

New (correct) xml:
<update from="" status="final" type="bugfix" version="1"><id>CL-BA-2013:0408</id><title>cifs-utils bug fix and enhancement update</title>...<references><reference href="http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=838606" id="838606" type="bugzilla">enable PIE and RELRO in cifs-utils binaries</reference></references>...</update>