Don't re-output bridgedb if it's already saved.

src/bin/bridgedb.rs

@@ -14,8 +14,7 @@ fn main() {
         serde_json::from_reader(bridgedb_infile).unwrap()
     } else {
         // create new bridgedb (implicitly generates keys)
-        BridgeDb::new()
-    };
+        let bridgedb = BridgeDb::new();
 
         // output full serialized bridgedb
         let mut bridgedb_outfile =
@@ -33,4 +32,8 @@ fn main() {
             serde_json::to_string(&bridgedb.pubkey).unwrap()
         )
         .expect("Failed to write to bridgedb_pubkey.json");
+
+        // return bridgedb
+        bridgedb
+    };
 }