PEP8: fix E712: comparison to False should be 'if cond is False:' or 'if not cond:'

PEP8: fix E712: comparison to False should be 'if cond is False:' or 'if not cond:'

Signed-off-by: Joe Guo <joeg@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>