async-ify more functions, and await completion

Where feasible I put the await at the end of the function to
minimize the impact on latency.

My motivation for this change: Eliminate a race condition in tests I
am writing.

src/node/db/AuthorManager.js

@@ -245,6 +245,6 @@ exports.removePad = async function(authorID, padID)
   if (author.padIDs !== null) {
     // remove pad from author
     delete author.padIDs[padID];
-    db.set("globalAuthor:" + authorID, author);
+    await db.set('globalAuthor:' + authorID, author);
   }
 }