Several FPP fixes
Several FPP fixes

FPP and SSF were broken due to the last commit because
yapio_perform_io() was still looping 'nranks' times searching for
populated md arrrays.

FPP filename mgmt is changed a bit and unlinking of FPP files works
again.

yapio_prepare_fpp_file_desc() is used to open the necessary file
descriptors before the next test runs.  If a file descriptor is already
open then no further action is required.

A setup timer has been added to the yapio_test_ctx_t for measuring the
time required for file opens.

00pauln00/yapio,00pauln00/yapio