build: use buildId as common context qualifier

Change-Id: I4dc202b3ab77d25ebbe5783f0ef6100cc10da235
Reviewed-on: http://gerrit.esdi-community.eu/3153
Tested-by: Jenkins <sitemple@igd.fraunhofer.de>
Reviewed-by: Simon Templer <simon.templer@igd.fraunhofer.de>