Fix sending interval of LLDP packets
As today LLDP is sent every 10000th execution of lldp task. During a normal operation that means 1 packets every 2 seconds. However, It can happen that LM32 is busy with other tasks like handling SNMP requests, then frequency of LLDP packets can be much, much longer. LLDP task shall check (monotonic!) time at every execution. When the the defined time elapsed it should send a LLDP packet.
It was never seen as a problem in operation since LLDP was not widely used yet.