ENYO-3506: Fixed broken cancellation for Build

ENYO-3506: fix broken build cancellation

1. Added (back) cancel button for first build step (Starting build)
2. Corrected all cancellation steps to correctly interrupt the build process

Refer to JIRA-3506(https://enyojs.atlassian.net/browse/ENYO-3506) for details.

Enyo-DCO-1.1-Signed-off-by: Francois Connetable <francois.connetable@hp.com>