Make ruby bundler in gate more resilient by only running
one job rather then multiple jobs in parallel and retry
the bundler install operation 3 times rather then failing
after first attempt for git requests and network issues.
* Use --jobs 1
* Use --retry 3
* Use --verbose to help with extension compile debugging
These are documented here: http://bundler.io/v1.5/bundle_install.html
Change-Id: Ic93ba6e7487ed92aa9cb984b6b8e7df08959b2aa
Closes-Bug: #1357439
65f1af17b7