Fix the testname of scenario

Duplicated testname in scenarios will result duplicated testname
by testscenarios, they can not be sorted in PY33 env, and will
induce TypeError:
TypeError: unorderable types: StackManagerNoPaginationTest() <
StackManagerNoPaginationTest()

Close-Bug #1243096

Change-Id: I4c02c9f3868495ec4399f795e864f26afc3d26b7