tests: Mark expected FreeBSD failures due to pr16699

FreeBSD's Host class doesn't yet return a list of running processes,
so 'platform process list' fails and attach by process name does not
work.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@187142 91177308-0d34-0410-b5e6-96231b3b80d8