This usually work on Fedora or other releases. I guess this is caused by some configurations specific in CentOS 6.6.
How to make CentOS 6.6 power off the console screen automatically?
You may try removing the
nomodeset. It plays the trick for me.
nomodeset? It disables Kernel Mode Set (KMS). KMS moves the initialization of the graphics mode from the X server to the kernel.
For some general information, please check: