Improve mock of python-redmine for pysflib unit tests.
Improve mock of python-redmine for pysflib unit tests.

A recent update of python-redmine made our unitests
long to run. This patch fix how we mocked the problematic
call to Redmine.

Change-Id: Iadcbe1dc29fc5e8ca86d91571fbdb0c565285090

enovance/software-factory,invenfantasy/software-factory,enovance/software-factory,invenfantasy/software-factory,invenfantasy/software-factory,invenfantasy/software-factory,enovance/software-factory,enovance/software-factory,invenfantasy/software-factory,enovance/software-factory