The expected behavior of the bottom LED is off when the the management interface is not enabled.
The LED should be as shown below. If management interface is enabled:
- Upper LED of the interface is on.
- Bottom LED of the interface is blinking.
POD15# configure management ethernet 13/1
POD15(conf-mgmt-ether)# enable 
If management interface is not enabled:
- Upper LED of the interface is on.
- Bottom LED of the interface is off,
POD15# configure management ethernet 13/1
POD15(conf-mgmt-ether)# no enable