LU-7812 tests: address race condition for sanity:120{e,f}

LU-7812 tests: address race condition for sanity:120{e,f}

By adding a delay between lock cancel and stat, it can avoid the
problem that the locks are still held by ldlm lock thread while
'cancel_lru_locks osc' is called.

Test-Parameters: trivial envdefinitions="ONLY=120e" testlist=sanity,sanity,sanity,sanity,sanity,sanity,sanity,sanity,sanity,sanity
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: I2095cb1df05ff45c2671edaed5a61bcdd4a56266
Reviewed-on: https://review.whamcloud.com/24811
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>