Add retry logic and cleanup for PipelinesBackend

Revision created by MOE tool push_codebase.
MOE_MIGRATION=7098


git-svn-id: http://appengine-pipeline.googlecode.com/svn/trunk@171 1742be92-6d41-bc97-00b7-290b722d530a
Expand the versions tollerated by our maven.

Revision created by MOE tool push_codebase.
MOE_MIGRATION=7099


git-svn-id: http://appengine-pipeline.googlecode.com/svn/trunk@172 1742be92-6d41-bc97-00b7-290b722d530a
Change RooJobInstance to use the delegate DisplayName.

Revision created by MOE tool push_codebase.
MOE_MIGRATION=7100


git-svn-id: http://appengine-pipeline.googlecode.com/svn/trunk@173 1742be92-6d41-bc97-00b7-290b722d530a