If we list eggs as eggs= of a zc.recipe.egg section, the scripts of these eggs
will be installed again.

This fixes this error while building:

    While:
      Installing extra-eggs.
    Error: The following paths are already installed by other sections: {'/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/soft/72b4c4e0472506664a0cb3cc44bbb0b2/bin/caucased-manage': 'caucase-eggs', '/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/soft/72b4c4e0472506664a0cb3cc44bbb0b2/bin/caucase-key-id': 'caucase-eggs', '/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/soft/72b4c4e0472506664a0cb3cc44bbb0b2/bin/caucase-updater': 'caucase-eggs', '/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/soft/72b4c4e0472506664a0cb3cc44bbb0b2/bin/caucase-rerequest': 'caucase-eggs', '/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/soft/72b4c4e0472506664a0cb3cc44bbb0b2/bin/caucase': 'caucase-eggs', '/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/soft/72b4c4e0472506664a0cb3cc44bbb0b2/bin/caucase-probe': 'caucase-eggs', '/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/soft/72b4c4e0472506664a0cb3cc44bbb0b2/bin/caucased': 'caucase-eggs'}