Fix the bug under mongo c driver v1.5
Fix the bug under mongo c driver v1.5

I misunderstand the interface when querying with projection
when the version of Mongo C Driver is lower than 1.5.

For reference, in case of Ubuntu 16.04, Mongo C Driver v1.3.1
will be installed, so when using 'Dedicated Bearer', v0.1.1
should be used because it does not work normally.

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