move copy_ledger() back into ledger.rs

Don't recover() for copy(), as copy() is already tolerant of things
    recover() guards against.  Note: recover() is problematic if the ledger is
    "live", i.e. is currently being written to.

src/fullnode.rs

@@ -143,14 +143,14 @@ impl FullNode {
     pub fn new_without_sigverify(
         node: TestNode,
         leader: bool,
-        ledger: &str,
+        ledger_path: &str,
         keypair: KeyPair,
         network_entry_for_validator: Option<SocketAddr>,
     ) -> FullNode {
         FullNode::new_internal(
             node,
             leader,
-            ledger,
+            ledger_path,
             keypair,
             network_entry_for_validator,
             true,