LU-1095 debug: conditionally print recovery status

Avoid printing non-sense messages like this when the recovery
code hasn't run. For example, this can occur when your starting
a new target for the first time.

  Lustre: lustre-OST0001: Recovery over after 22277843:04,
  of 0 clients 0 recovered and 0 were evicted.

Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Change-Id: Ib4bd8783c0c17aa15052fc9b9cf78e18274b2783
Reviewed-on: http://review.whamcloud.com/4043
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>