PHP-999: Fix RP support for inline mapReduce
PHP-1000: Allow "mapreduce" and "mapReduce" command names in RP check

"mapReduce" is the canonical command name, and the server allows either to be used.
Use canonical mapReduce command name in PHP-535 test

Since tests may frequently be used as usage examples, it'd be helpful if we stuck to using the proper command name here unless we're explicitly testing for another case (e.g. PHP-1000 and the PHP-999 test case).
Merge pull request #598