LU-5768 target: Revert the test part of the LU-5579 fix

This patch reverts the test part, including the tgt_enqueue() fault
injection, of the LU-5579 fix (d29c0438).  These changes cause
replay-single 52 and 73b to fail frequently.

Change-Id: I63c9210ddd4165cf587272e4216cd39dc608f976
Signed-off-by: Li Wei <wei.g.li@intel.com>
Reviewed-on: http://review.whamcloud.com/12390
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>