tests: Support idm failure injection

tests: Support idm failure injection

When the drive failure occurs, the IDM lock manager and lvmlockd should
handle this case properly.  E.g. when the IDM lock manager detects the
lease renewal failure caused by I/O errors, it should invoke the kill
path which is predefined by lvmlockd, so that the kill path program
(like lvmlockctl) can send requests to lvmlockd to stop and drop lock
for the relevant VG/LVs.

To verify the failure handling flow, this patch introduces an idm
failure injection program, it can input the "percentage" for drive
failures so that can emulate different failure cases.

Signed-off-by: Leo Yan <leo.yan@linaro.org>