refs #5197 Fix a couple of bugs (off by true, and missing braces around if statement) with not reserving memory for put-loader
Also only call toku_txn_require_checkpoint_on_commit(tokutxn) once (instead of N times)

git-svn-id: file:///svn/toku/tokudb@45351 c7de825b-a66e-492c-adef-691d508d4ae1