iec: Stop upstream job if IEC installation fails

iec: Stop upstream job if IEC installation fails

Previously, we were using a single `trigger-builds` builder, which as
a consequence led to running all downstream projects even if the first
one (installing the IEC platform) failed.

Switch to using 2 different `trigger-builds` builders so:
- if IEC installation fails, no other downstream jobs are executed and
  the upstream (parent) job is marked as failed;
- if any other downstream job (except SEBA install/test jobs) fails,
  the upstream (parent) job is marked as failed/unstable, but all other
  downstream jobs are still executed (so we can still install/test SEBA
  and destroy the IEC installation at the end even if the 'validation'
  job failed);

Change-Id: I946c5bc9f2cc35afcbeb64d954beb10f3281fc11
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>