Add FreeBSD failure decorator for TestCallStopAndContinue

The testrun now completes successfully on my FreeBSD 11.0-CURRENT
laptop.  There are some intermittent failures on the FreeBSD buildbot
still, which should be addressed in later commits.

llvm.org/pr20274


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@212878 91177308-0d34-0410-b5e6-96231b3b80d8