Showing the full name in flow __str__() isn't expecially
helpful and clutters up graphviz usage and similar so if a taskflow
built-in pattern is stringified just use the short name (that does
not start with taskflow.patterns instead of the full long name).
Change-Id: Icd8c26eab1e19d6ecf9c4e8e82e6d6902ce5b6ea