workaround odd dnf issues with samba-4.19.0-0.3.rc2 updates
    
    dnf seems to have some odd trouble with these updates. It
     really wants to use the older 2.rc2 builds, even though there
    doesn't seem to be any actual *problem* with the 3.rc2 builds.
    
    For the samba server test, passing `--best` to dnf seems to be
    enough to make it use the .3.rc2 builds. For the FreeIPA tests,
    we have to do a second pass with `--best` after the initial
    install.
    
    It's weird that we have to do this, but to get these updates
    through - because there doesn't really seem to be a problem
    here - let's do it. They will replace the 2.rc2 builds in the
    main F39 and Rawhide trees once they land in 'stable' so the
    problem shouldn't persist.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>