Energy model: fixing sysbench taskset failure

Make sure when migrating sshd to root cgroup also migrate their
children, including the bash for the wa session. So the subsequent
processes kicked off from that shell can be taskset to any cluster.

wlauto/common/linux/device.py

@@ -972,7 +972,7 @@ class LinuxDevice(BaseLinuxDevice):
         # result should be a column of PIDs with the first row as "PID" header
         result = self.execute('ps -C {} -o pid'.format(process_name), check_exit_code=False).strip().split()
         if len(result) >= 2:  # at least one row besides the header
-            return result[1:]
+            return map(int, result[1:])
         else:
             return []