armband: project: inherit {installer}-defaults

armband: project: inherit {installer}-defaults

While at it, also do the following:
- revert previous addition of "armband-defaults" in
  opnfv/installer-params.yml, no longer needed;
- remove Josep from failure mail recipient list, armband@enea.com
  is already forwarded to all of us;
- add CACHE_DIRECTORY variable for enabling build cache;

TODO (left for future rework):
- rename build and deploy jobs to include installer info, e.g.
  "armband-fuel-build-...", preparing for more installers;
- move "installer" parameter to fuel jobs only instead of having
  it as a global param;

Change-Id: I2e6cc43484576bd6569605a7c9e60f6fe64f435b
Signed-off-by: Josep Puigdemont <josep.puigdemont@enea.com>
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>