SERVER-5389 don't "attempt" so often

jstest.attempt() is used to pound on something until a condition is met.
Polling every half a second isn't gaining us much, but it is littering
build logs with a lot of extra output (the functions passed to this
function tend to print things).  With this submit I am reducing the clutter
by 4x.

src/mongo/shell/utils.js

@@ -1172,7 +1172,7 @@ jsTest.isMongos = function(conn) {
 jsTest.attempt = function( opts, func ) {
     var timeout = opts.timeout || 1000;
     var tries   = 0;
-    var sleepTime = 500;
+    var sleepTime = 2000;
     var result = null;
     var context = opts.context || this;