This commit added a BatchSize option for Database#ListCollections but the legacy listCollections code path for server version 2.6 does not honor it (see here). We should fix that by using the cursor.batchSize command field to set the NumberToReturn field in the constructed OP_QUERY message similar to the legacy listIndexes logic.

Additionally, GODRIVER-1934 is adding a test for getMore/killCursors commands to mongo/integration/database_test.go. Due to this bug, the test has to be skipped on 2.6, so the work for this ticket should also unskip it.