SERVER-8382

Added authentication to admin for serverStats access when credentials
are passed in.

Signed-off-by: Ian Whalen <ian.whalen@gmail.com>
SERVER-8382

Added authenticating to admin for benchRun thread.
Fixed formating of error messages on failure.

Signed-off-by: Ian Whalen <ian.whalen@gmail.com>
SERVER-8382

Updating format as per codereview and updating uasserted code

Signed-off-by: Ian Whalen <ian.whalen@gmail.com>
SERVER-6388 partial

With server-8382 bench_test1.js should send (or not send) same
username/password for all benchRun calls.

Signed-off-by: Ian Whalen <ian.whalen@gmail.com>