[master] for usage output be clear about verbose

This was discussed on jabber.

src/bin/auth/main.cc

@@ -87,7 +87,7 @@ usage() {
     cerr << "Usage:  b10-auth [-u user] [-nv]"
          << endl;
     cerr << "\t-n: do not cache answers in memory" << endl;
-    cerr << "\t-v: verbose output" << endl;
+    cerr << "\t-v: verbose logging (debug-level)" << endl;
     exit(1);
 }