xen/processor-passthru: threads aren't suppose to leave on their own.

xen/processor-passthru: threads aren't suppose to leave on their own.

otherwise you get this:
WARNING: at /home/konrad/ssd/linux-uek-2.6.39/kernel/workqueue.c:1217 worker_enter_idle+0xd3/0x140()
eth1: no IPv6 routers present
Hardware name: System Product Name
Modules linked in: processor_passthru xen_evtchn iscsi_boot_sysfs iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi libcrc32c crc32c nouveau mxm_wmi video sg sd_mod atl1c e1000e radeon ahci libahci libata fbcon tileblit font ttm bitblit scsi_mod softcursor drm_kms_helper wmi xen_blkfront xen_netfront fb_sys_fops sysimgblt sysfillrect syscopyarea xenfs xen_privcmd [last unloaded: dump_dma]
Pid: 525, comm: kworker/1:1 Not tainted 2.6.39 #5
Call Trace:
 [<ffffffff8107c97a>] warn_slowpath_common+0x7a/0xb0
 [<ffffffff8107c9c5>] warn_slowpath_null+0x15/0x20
 [<ffffffff810920b3>] worker_enter_idle+0xd3/0x140
 [<ffffffff81094cd0>] worker_thread+0x230/0x420
 [<ffffffff81094aa0>] ? manage_workers+0x220/0x220
 [<ffffffff81099596>] kthread+0x96/0xa0
 [<ffffffff81576d24>] kernel_thread_helper+0x4/0x10
 [<ffffffff81575e33>] ? int_ret_from_sys_call+0x7/0x1b
 [<ffffffff8156f9a1>] ? retint_restore_args+0x5/0x6
 [<ffffffff81576d20>] ? gs_change+0x13/0x13

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>