cleaned up transaction in hot index #1035
removed read lock during build phase of hot index #1035
refs #1035 Hold the oplock around a hot index build to prevent stepdown
refs #1035 prevent multikey bit transitions during a hot index. further,
prevent reIndex. both of these may require collection close on rollback
and so cannot run while the index is still provisional.
Merge pull request #1073 from Tokutek/hot-index-locking

Hot index locking

fixes #1035