[LTP] [RFC] shell wrappers for tst_checkpoint

[Stanislav Kholmanskikh]

Hi!

There is a need to use the tst_checkpoint interface from shell, but
we don't have wrappers for it (yet).

Patch 1 of the series contains one possible implementation for that,
patch 2 - an example of usage in the context of the memcg_functional test case.

I'd like to get some feedback from LTP users.

My primary concern is about two issues:

1. The new test API for C is cool and takes the responsibility on
   maintaining the infrastructure for tst_checkpoint. However, I couldn't find
   a way to implement something similar in shell, so I switched back to using
   two separate functions for that - TST_CHECKPOINT_SETUP, TST_CHECKPOINT_CLEANUP.

   There may be a better way...

2. What is the best location for the new supplemental binaries (tst_checkpoint_wait,
tst_checkpoint_wake)? tools/apicmds/ltpapicmd.c or separate source files in
testcases/lib/ (similar to tst_sleep)?

Thanks.