[JIRA] (OVIRT-1066) Fix error handling in the experimental flow Groovy script

Fix error handling in the experimental flow Groovy script --------------------------------------------------------- Key: OVIRT-1066 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-1066 Project: oVirt - virtualization made easy Issue Type: Improvement Components: oVirt CI Reporter: Barak Korren Assignee: infra Error handling is not done in a consistent manner in the Experimental flow Groovy script. Sometime exceptions are used, other times the 'currentBuild.result' variable is used and exceptions are actually suppressed. This right way seems to be to use exceptions. Currently various things seem to be broken like properly marking that a build failed in the pipeline stage display plugin.