Fixing recommendations

nearest uses closest by ping time which is not what fastest implies.

The recommendation on increasing throughput is highly misleading - there is no way that someone can expect reduced disk I/O and increased throughput by reading from nearest secondary unless their specific problem was something extremely specific (and uncommon!)

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2339 new steps format: enable authentication

          plus additional content