Enable ignore_cache flag on jenkins_jobs.ini

Parses jenkins_jobs.ini to look for an ignore_cache flag.
If ignore_cache command line option is sent, it takes priority
over the jenkins_jobs.ini configuration.

Change-Id: I88f1ce1aa0d3e0ad25d592d3ca44a022ec9249c3
Closes-Bug: #1193444
Merge "Enable ignore_cache flag on jenkins_jobs.ini"