The cobertura plugin does not play well with maven builds when a maven release is performed

See https://issues.jenkins-ci.org/browse/JENKINS-4399 where teilo says "Personally I consider this a defect in the corbetrura and clover plugins that
fails the build if the report isn't there - it should check that the mojo was run during the build and only fail if it ran and the report was empty."

The plugin works fine for a normal maven build, but when using the "Jenkins Maven Release Plug-in Plug-in" to release a maven build, the cobertura reports would/should not normally be generated but the cobertura plugin fails the release build.

For example:
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] aaa-client-parent ............................. SUCCESS [1:30.340s]
[INFO] aaa-client .................................... SKIPPED cobertura report created here normally but skipped for a release
[INFO] aaa-client-integration-test ................... SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1:31.727s
[INFO] Finished at: Thu Feb 02 12:57:08 GMT 2012
[INFO] Final Memory: 17M/146M
[INFO] ------------------------------------------------------------------------

Publishing Cobertura coverage report...
No coverage results were found using the pattern '**/target/site/cobertura/coverage.xml' relative to '...'. Did you enter a pattern relative to the correct directory? Did you generate the XML report(s) for Cobertura?
Build step 'Publish Cobertura Coverage Report' changed build result to FAILURE