test1572 doesn't really test #1572 yet, but it did point out #1577.  Now we are more careful about memory management in the rollback logs, so that we don't blow out memory.  Fixes #1577.  Refs #1572.

git-svn-id: file:///svn/toku/tokudb@10397 c7de825b-a66e-492c-adef-691d508d4ae1