package.xml shoud not contain dependencies tag when HF01 is built

The specific use case for HF01 is not taken into account and will generate the following tag:

  <dependencies>
     <package>nuxeo-${TARGET_BRANCH}-@PREVIOUSHOTFIX@:${LATEST_PKG_REV}</package>
  </dependencies>

There should be a test on LATEST_PKG_ID result. If it is empty then no dependencies tag needed.