Problem Description :
In case of you renamed a Failover Cluster in Failover Cluster Manager which is connected to a SCVMM 2012 R2 you will see that the renaming will not be reflected in SCVMM 2012 R2.
Under these circumstances you can basically rename the Failover Cluster over the VirtualManagerDB > dbo.tbl_ADHC_HostCluster > Name Column as follows.
1) Connect to the VirtualManagerDB via SSMS.
2) Expand tables and navigate to dbo.tbl_ADHC_HostCluster.
3) And rename the Failover Cluster under the names column.
Good luck !