Rename QUOTAS section for quotas

Quotas section in neutron.conf was renamed from [QUOTAS]
to [quotas] in Havana.

Closes-bug: #1341657
Change-Id: I757a804ac846cc96a80bd76994d274b890885625
(cherry picked from commit 4ab8a0e2738d23f3f276804607d7523797e10de0)