recompute_head executes only after the first epoch

[rodrigo-o]

On syncing, the head root is set to the checkpoint state block root, but never recalculated throughout the current epoch, it statrs to be recalculated just after the initial one has ended.

This could be seen in the logs, as it never shows the root change for the first couple of minutes:

INFO 19:09:21.187 [Fork choice] Adding new block slot=10997347 root=0x1ed..752a
INFO 19:09:35.494 [Fork choice] Block processed. Recomputing head. 
INFO 19:09:35.703 [Fork choice] Added new block slot=10997347 root=0x1ed..752a
INFO 19:09:35.704 [Fork choice] Recomputed head slot=10997344 root=0x61a..c919
INFO 19:09:35.704 [Fork choice] Block processing time: 14.307s | Recompute head time: 0.175s
 
INFO 19:09:35.706 [Fork choice] Adding new block slot=10997348 root=0x674..df69
INFO 19:09:50.037 [Fork choice] Block processed. Recomputing head. 
INFO 19:09:50.291 [Fork choice] Added new block slot=10997348 root=0x674..df69
INFO 19:09:50.291 [Fork choice] Recomputed head slot=10997344 root=0x61a..c919
INFO 19:09:50.291 [Fork choice] Block processing time: 14.331s | Recompute head time: 0.206s