The controller looks like it is reporting correctly, so it does seem to just be an SNMP issue. I will report the issue.
I updated OpenManage Server Administrator from 7.4 to 8.1 on Centos6 Now SNMP module  ( StorageManagement-MIB::virtualDiskDiskCachePolicy or .1.3.6.1.4.1.674.10893.1.20.140.1.1.26) shows INTEGER: 2 (Disabled) but from console (omreport storage vdisk controller=0) Disk Cache Policy                 : Enabled Reboot, chanling policy(omconfig storage vdisk action=changepolicy) did not help. Is it bug? 
OpenManage 8.1.0 snmp