Improve pod annotation mgmt with multiple events

[xenserverarmy]

• Resolve race conditions wrt short lived pods
• Rescan if pod only representation of an image is encountered
• Add sweeper pod annotation model to catch pods which couldn't be annotated upon creation

Test environments:

• OCP 3.5, OCP 3.6, OCP 3.7, Kube 1.8 (Heptio)

Test scenarios:

• Scale pod up, observed pod annotations
• Scale pod down and the up and observe correct annotations
• Upgrade version of ose_scanner and observe pods without image streams are correctly annotated
• In build pipeline observe builder and deployer pods are identified and annotated
• When git trigger occurs, builder pods are identified and annotated

[jayunit100]

quick review, minor nit function comments otherwise LGTM