Refactor syncer initialization to separate go-routine

[gupadhyaya]

currently the syncer is initialized after the genesis block is produced by manually initializing the store and starting the syncer (syncer needs the genesis block to be available in store for successful init). this manual initialization interfere with Broadcast which results in validation failed (known header: '1' <= current '1') #969. Ideally, we should broadcast (which self stores the block/header), which then should trigger the syncer to initialize. This would eliminate double init.

[ThanhNhann]

Hi @gupadhyaya, can I handle this issue ?