Add an option for device model to disable key repeat.
On slow network, when creating a vmx guest remotely,
the key repeat feature may make it hard to even type
the user name and password to login in to guest OS.

Signed-off-by: Eddie, Dong <eddie.dong@intel.com>
Signed-off-by: Xiaofeng, Ling <xiaofeng.ling@intel.com>