AP_DroneCAN: DNA_Server: make lower level database tasks private

All the higher level database operations need to be locked for the whole
duration of the operation, so nobody should be using the lower-level
tasks or raw read/write functions. We can also remove the locks from
them.

The database can now safely be used by multiple servers.

libraries/AP_DroneCAN/AP_DroneCAN_DNA_Server.cpp

@@ -74,7 +74,6 @@ void AP_DroneCAN_DNA_Server::Database::readNodeData(NodeData &data, uint8_t node
         return;
     }
 
-    WITH_SEMAPHORE(sem);
     storage->read_block(&data, NODEDATA_LOC(node_id), sizeof(struct NodeData));
 }
 
@@ -85,7 +84,6 @@ void AP_DroneCAN_DNA_Server::Database::writeNodeData(const NodeData &data, uint8
         return;
     }
 
-    WITH_SEMAPHORE(sem);
     storage->write_block(NODEDATA_LOC(node_id), &data, sizeof(struct NodeData));
 }
 

libraries/AP_DroneCAN/AP_DroneCAN_DNA_Server.h

@@ -47,6 +47,7 @@ class AP_DroneCAN_DNA_Server
         // handle the allocation message. returns the new node ID.
         uint8_t handleAllocation(uint8_t node_id, const uint8_t unique_id[]);
 
+    private:
         //Generates 6Byte long hash from the specified unique_id
         void getHash(NodeData &node_data, const uint8_t unique_id[], uint8_t size) const;
 
@@ -62,7 +63,6 @@ class AP_DroneCAN_DNA_Server
         //Finds next available free Node, starting from preferred NodeID
         uint8_t findFreeNodeID(uint8_t preferred);
 
-    private:
         //Look in the storage and check if there's a valid Server Record there
         bool isValidNodeDataAvailable(uint8_t node_id);