Description of problem:
Channel information serialized into an XML file during channel export contains
errata information in two places:
1. /rhn-satellite/rhn-channels/rhn-channel/@channel-errata
2. /rhn-satellite/rhn-channels/rhn-channel/rhn-channel-errata/errata

While the first is being exported correctly (i.e the list of erratas
is exported either by rhnErrata.last_modified or rhnChannelErrata.modified;
based on what was specified on command line), the second list of erratas
is always being exported based on rhnChannelErrata.modified, regardless
of what was specified on command line.

This naturally poses a problem since:
1. List of the erratas falling into the two intervals will not always match
2. satellite-sync searches for the exported erratas based on the information
contained in the second list

A synchronization error occurs, when the second list contains an errata
which is not contained in the first list.

Version-Release number of selected component (if applicable):
spacewalk-backend-1.2.13-38

How reproducible:
Always

Steps to Reproduce:
1. Satellite 5.4, redhat-rhn-proxy-4.2-as-i386-4 synced
2. rm -rf /var/cache/rhn/xml-*;
3. rhn-satellite-exporter -c redhat-rhn-proxy-4.2-as-i386-4 \
   -d wherever --start-date 20090611000000 --end-date 20110407000000
4. cd wherever
5. xmllint -format channels/redhat-rhn-proxy-4.2-as-i386-4/channel.xml.gz
6. Check whether the erratas contained in the first and second list match
7. Make sure you're able to import the dump
  
Actual results:
The lists do not match, the sync fails with following error:

Exception Handler Information
Traceback (most recent call last):
  File "/usr/bin/satellite-sync", line 143, in main
    return satsync.Runner().main()
  File "/usr/share/rhn/satellite_tools/satsync.py", line 226, in main
    ret = method()
  File "/usr/share/rhn/satellite_tools/satsync.py", line 336, in _step_download_errata
    return self.syncer.download_errata()
  File "/usr/share/rhn/satellite_tools/satsync.py", line 1741, in download_errata
    stream_loader.process(chunk)
  File "/usr/share/rhn/satellite_tools/satsync.py", line 2100, in process
    stream = self.disk_loader.load()
  File "/usr/share/rhn/satellite_tools/xmlDiskSource.py", line 41, in load
    return self._loadFile(filename)
  File "/usr/share/rhn/satellite_tools/xmlDiskSource.py", line 59, in _loadFile
    raise MissingXmlDiskSourceFileError("unable to process file %s" % filename)
MissingXmlDiskSourceFileError: unable to process file /var/satellite/channel-dumper/dump-iso/errata/5/rhn-erratum-4835.xml

Expected results:
The lists match, it is possible to import the dump.

Additional info:
N/A