PT_CONTINUE and PT_STEP are process-scope on FreeBSD

Although ptrace() can be passed a PID or TID for PT_CONTINUE and PT_STEP,
the kernel operates on all threads in the process in both cases.  (See
the FOREACH_THREAD_IN_PROC in FreeBSD's sys_process.c:kern_ptrace.)

Make this clear by using the PID from the ProcessMonitor instance.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@195656 91177308-0d34-0410-b5e6-96231b3b80d8