RPM Support

A report from upstream katello (https://projects.theforeman.org/issues/25529) indicates that pulp generates a repomd.xml file that claims to use the checksum type that has been set on the publisher, but in fact is not using that:

In this example it purports to have used a sha1 checksum, but in fact its actually a sha256 checksum:

  <data type="modules">
    <location href="repodata/824ffe238f202a0612ecbb2b0c0459dc289a7ef47adb1f26406453d41f476449-modules.yaml.gz"/>
    <timestamp>1542811864</timestamp>
    <size>33</size>
    <checksum type="sha1">824ffe238f202a0612ecbb2b0c0459dc289a7ef47adb1f26406453d41f476449</checksum>
    <open-size>0</open-size>
    <open-checksum type="sha1">da39a3ee5e6b4b0d3255bfef95601890afd80709</open-checksum>
  </data>

To reproduce:

1. create and sync a yum repository
2. set a checksum type of sha1
3. publish the repository