LU-15636 test: add iabf

LU-15636 test: add iabf

Usage: [IABF_OPTIONS...] iabf [INIT] --- A --- B --- [FINI] ---

Initialize, run tasks A and B with various overlaps, and Finalize.

Command lines for INIT, A, B, and FINI are terminated by ---.
If INIT or FINI is empty then it will be skipped.
If INIT or FINI fail then we exit immediately with status 1.

For delay = $IABF_DELAY_BEGIN_NS; delay < $IABF_DELAY_END_NS;
		delay += $IABF_DELAY_STEP_NS
  Run initializer (INIT).
  In parallel: Fork, delay *, and exec processes A and B.
    If delay is negative then delay A by abs(delay) ns.
    Otherwise delay B by delay ns.
  Wait for A and B to terminate.
  Run finilizer (FINI).

See lustre/tests/iabf/README for more information.

Test-Parameters: trivial
Change-Id: I97920e082a7a5bec458c805c507b4fefb448427b
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/46744
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>