JAVA-1156: Properly ensure that none of the server-defined limits on the write commands are exceeded.
 There is one limit for the number of items that are allowed in each command (maxWriteBatchSize from ismaster).
 There is a second limit for the number of bytes in the encoded message (maxBsonObjectSize from ismaster),
 with an exception for a write command containing just a single item, which is allowed to exceed this length.