Indicates the state of the interface. It is called status
because this is what it was called in the rfc.
FR_STATUS_RUNNING is the sate after the circuit is up (either LMI
successful or there is no DLCMI and the system just comes up).
FR_STATUS_FAULT is a transient state indicating that errors have
caused the circuit to be disabled until DLCMI recovery.
FR_STATUS_INITIALIZING is a transient state indicating that
the interface is trying to come up.
FR_STATUS_NOTPRESENT indicates that the interface is not present.
Likely this will never be seen except upon initial
configuration.