Perform thread lookup after RefreshStateAfterStop()

This fixes a crash on FreeBSD



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@189607 91177308-0d34-0410-b5e6-96231b3b80d8
Fix FreeBSD build after r189295


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@189608 91177308-0d34-0410-b5e6-96231b3b80d8