test/make: Ignore abidiff's exit status

Upon running abidiff to get the list of impacted interfaces it seems
to exit with != 0 status. This triggers errexit causing the script
to exit in the middle of processing the lib files so we don't get
the full picture of all potentially impacted files. Ignore the
exit status in this case and allow the loop to go through all the
.sos.

Signed-off-by: Michal Berger <michalx.berger@intel.com>
Change-Id: I7edc5122161b0927fdd9a918571419f32fd46dac
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/7815


Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Paul Luse <paul.e.luse@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>