selftest/flapping: mark samba4.blackbox.gentest as flakey

selftest/flapping: mark samba4.blackbox.gentest as flakey

https://git.samba.org/autobuild.flakey/2012-03-14-1307/samba4.stdout

    [1228/1371 in 1h19s] samba4.blackbox.gentest(dc)
    UNEXPECTED(failure): samba4.blackbox.gentest(dc).gentest
    REASON: _StringException: _StringException: seed=1
    Connecting to \localdcest1 as Administrator - instance 0
    Connecting to \localdcest1est1 as Administrator - instance 1
    Connecting to \localdcest1est2 as Administrator - instance 0
    Connecting to \localdcest1est2 as Administrator - instance 1
    0
    OPEN num_open_handles=1 h=0 (gentest\foo4)
    Notify count inconsistent 1 0
    Failed at operation 88 - MKDIR
    gentest failed

I saw this more than 10 times in the last year already.

metze