Small fixes detected by clang analyzer.

Small fixes detected by clang analyzer.

 - log: mark `fatal*()` function as noreturn
 - event: insert client in the list after its creation
 - lldpcli: avoid confusion by initializing cargc to 0
 - lldpd: avoid ambiguous use of strlen() in initialization
 - lldp/edp: fix memory leaks
 - tokenizer: fix a memory leak in low memory condition
 - cdp: don't accept too short TLV for port description