Fix protobuf serialization of path field.
Fix protobuf serialization of path field.

BelledonneCommunications/flexisip,gale320/flexisip,biddyweb/flexisip,gale320/flexisip,gale320/flexisip,gale320/flexisip,BelledonneCommunications/flexisip,biddyweb/flexisip,biddyweb/flexisip,BelledonneCommunications/flexisip,biddyweb/flexisip,BelledonneCommunications/flexisip