LU-8649 recovery: print some useful messages in recovery

LU-8649 recovery: print some useful messages in recovery

To make it more clear to the admins that recovery won't start
until the first client connects, this patch prints the following
useful messages in recovery, in case the admins are waiting for
recovery to complete:
- a console message every 10 minutes or so, and
- adding status WAITING_FOR_CLIENTS to /proc recovery_status file

Lustre-change: https://review.whamcloud.com/30656
Lustre-commit: 614e0def46be607cc53bbec9624d5b039068ba7c

Change-Id: I03d37b4c00a799a1fd651b8d60cdbceed807cea1
Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/30811
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>