Update OWNERS

pkg/volume/cinder/OWNERS

 approvers:
 - jsafrane
-- spothanis
 reviewers:
+- anguslees
+- justinsb
+- rootfs
+- brendandburns
 - thockin
+- smarterclayton
+- deads2k
+- brendandburns
+- derekwaynecarr
 - bprashanth
 - pmorie
 - saad-ali
 - justinsb
-- pwittrock
-- timstclair
 - jsafrane
-- dims
 - rootfs
-- markturansky
-- fgrzadkowski
 - jingxu97
-- fabioy
-- resouer
-- david-mcmahon
-- swagiaal
-- chakri-nelluri
-- goltermann
-- screeley44
+- rkouj
+- msau42