src/locktest: Audit all debug output

src/locktest: Audit all debug output

Audit all the debug output to be clear on what failed so that we can
remove the debug flag from the script.

Specifically, remove the need for a debug flag on system call error
output.  This helps to indicate what happened when an individual test
step fails.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>