LU-5816 target: don't trigger watchdog waiting in recovery

LU-5816 target: don't trigger watchdog waiting in recovery

In target_recovery_thread, the process should not be considered
to be "blocked state" if it was waiting something to happen,
otherwise, the kernel watchdog will print:

task tgt_recov:19764 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
tgt_recov     D 0000000000000003     0 19764      2 0x00000000
Call Trace:
check_for_clients+0x0/0x70 [ptlrpc]
target_recovery_overseer+0x9d/0x230 [ptlrpc]
exp_connect_healthy+0x0/0x20 [ptlrpc]
autoremove_wake_function+0x0/0x40
target_recovery_thread+0x0/0x1920 [ptlrpc]

Change-Id: Ic1ad4dce1df974dd99e0b28cee211de173d178e5
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: http://review.whamcloud.com/12672
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>