These are fixes for SERVER-17587. The basic idea is to rely on meta tracking to take care of flushing the metadata during any operation that needs to close a dirty tree.

Note that this change relies on __wt_meta_track_off making the metadata stable. That function checkpoints the metadata if logging is not enabled. It is sufficient to fix the included test case, but deserves careful review to determine whether it does enough to make the metadata stable on disk before old checkpoints are freed in general. (I suspect it doesn't, today, but keep in mind that we're closing a single tree for some exclusive operation such as verify – there is no concurrent eviction).