LU-1166 recovery: don't leak a connected client counter.

LU-1166 recovery: don't leak a connected client counter.

target_handle_connect vs client eviction race may leak a
connected client counter and some evicted clients will counted twice.

Xyratex-bug: MRP-451

additional changes to complete pieces left out of previous commit

Signed-off-by: Alexey Lyashkov <alexey_lyashkov@xyratex.com>
Signed-off-by: Bob Glossman <bogl@whamcloud.com>
Change-Id: I4218fcc8f5eacc8ddd61fe5d6d22ec4d5eace00a
Reviewed-on: http://review.whamcloud.com/2874
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>