[FIXED JENKINS-22856] Uses AbstractProject instead of Item in Descriptor.doCheckProjects. It can be get confused with JobPropertyImpl.getJobOverrides or /lib/form/withCustomDescriptorByName.
Merge pull request #68 from ikedam/feature/JENKINS-22856_AncestorForDoCheckProjects

[JENKINS-22856] Uses AbstractProject instead of Item in Descriptor.doCheckProjects