Remove rendundant parentheses of cfg help strings

There is a hacking review https://review.openstack.org/#/c/74493/.
That makes me be aware we maybe have rendunant parentheses.
We'd better clean the parentheses, Python will handle that well.

Change-Id: Ib29f995feed45d71000f333a2cc7d14b0efcb0d5
Merge "Remove rendundant parentheses of cfg help strings"