Description of problem:
Yum is repeatedly downloading primary.sqlite.bz2 when old repomd.xml downloaded
from a mirror. This happens on "yum clean" command too. I am unable to clean
metadata with yum commands, only with:
  rm -rf /var/cache/yum/*
command.

Version-Release number of selected component (if applicable):
yum-3.2.4-2.fc7

How reproducible: sometimes, when wrong mirror selected


Steps to Reproduce:
1. try to update from old or very new mirror. May be you can simulate this by
touching /var/cache/yum/fedora/repomd.xml file.
2. yum update
3. yum clean
  
Actual results:
Yum is searching for primary.sqlite file corresponding to it's repomd.xml (or
other file?)

[root@hnedy ~]# yum clean all
primary.sqlite.bz2        100% |=========================| 3.8 MB    00:06
ftp://fedora.bu.edu/releases/7/Everything/i386/os/repodata/primary.sqlite.bz2: [
Errno -1] Metadata file does not match checksum
Trying other mirror.
primary.sqlite.bz2        100% |=========================| 3.8 MB    00:14
http://ftp.kddilabs.jp/Linux/packages/fedora/releases/7/Everything/i386/os/repod
ata/primary.sqlite.bz2: [Errno -1] Metadata file does not match checksum
Trying other mirror.
primary.sqlite.bz2        100% |=========================| 3.8 MB    00:00
http://ftp.upjs.sk/pub/fedora/linux/releases/7/Everything/i386/os/repodata/prima
ry.sqlite.bz2: [Errno -1] Metadata file does not match checksum
Trying other mirror.
primary.sqlite.bz2        100% |=========================| 3.8 MB    00:08
http://ftp.usf.edu/pub/fedora/linux/releases/7/Everything/i386/os/repodata/prima
...

Expected results:
Yum data cleanup.

Additional info:
Same problem for "yum clean metadata".
This command downloads more unnecessary data from mirrors, generating high
mirror loads on client and server side. May be yum can detect this after
downloading 2-3 files and re-download repomd.xml from same server. I think "yum
clean all" with no network access is recommended.