This breaks tailable cursors and it's not that important anyway.

Revert "fixes #731 Virtualize checkEnd() and implement it as a no-op for"

This reverts commit 332fc1553bc3ab12a0c4213b3abe63b94227d753.
Merge branch 'master' of github.com:Tokutek/mongo
fixes #852 Disable inserts into a capped collection in a multi-statement
transaction, add a test for such, and add a simple tailable cursor test.