LU-1999 tests: check LW client eviction in logs

LU-1999 tests: check LW client eviction in logs

A lightweight client can reconnect rather quickly after a server
restart (they are allowed to reconnect during recovery), which
confuses wait_client_evicted().
A more reliable check is to search for eviction message in the log.

Signed-off-by: Johann Lombardi <johann@whamcloud.com>
Change-Id: Idb5fda48c7d73c465c8d69c18f2040d5fa08e3ba
Reviewed-on: http://review.whamcloud.com/4069
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>