trivial: Correct class name for BaseVolumeQuotasAdminTestJSON

We are prefixing these class names with "Base" even though they
runs tests [0]. Nothing inherits from either as well, so we
should be able to safely drop "Base" prefix from both [1][2].

[0] e.g. http://logs.openstack.org/16/599316/1/check/tempest-full/591615d/job-output.txt.gz#_2018-09-03_09_27_59_970390
[1] http://codesearch.openstack.org/?q=BaseVolumeQuotasAdminTestJSON&i=nope&files=&
[2] http://codesearch.openstack.org/?q=BaseVolumeQuotasNegativeTestJSON&i=nope&files=&repos=

Change-Id: If0fb302b86c3f15b6107ed1fc1e390eb101e9774
2 files changed