Fix P2P illegitimate kicks
When receiving locators from a different peer in full or rolling mode, if this peer happens to have a one block difference with the node, its locator's steps would be an empty list and would fall in the Too_short_locator
error which would result in a kick... this fixes this.
It should also fixes the spurious resulting messages such as :
Jul 31 12:32:22 - validator.peer_41051: Worker started for NetXdQprcVkpa:idqbtrsEJTsC
Jul 31 12:32:26 - validator.peer_41051: Worker terminated [NetXdQprcVkpa:idqbtrsEJTsC]
Jul 31 12:32:27 - validator.peer_41052: Worker started for NetXdQprcVkpa:idtRWqdab3Vp
Jul 31 12:32:43 - validator.peer_41052: Worker terminated [NetXdQprcVkpa:idtRWqdab3Vp]
Jul 31 12:32:54 - validator.peer_41050: Worker terminated [NetXdQprcVkpa:idqUc9LXTUEW]
Jul 31 12:33:06 - validator.peer_41053: Worker started for NetXdQprcVkpa:idskBJ53hysi
Might be indirectly related to #559 (closed)