We were creating the turtle file, and if it didn't previously exist we'd create
the metadata file.  If we crashed between those two steps, we'd fail the next
open because the turtle file existed but the metadata file didn't.

Restructure so we don't create the turtle file until we finish creating the
metadata file (and loading any hot backup), that way if the turtle file exists,
everything else is known to be good.

Ref #554.
Merge branch 'develop' into turtle-race
Merge pull request #555 from wiredtiger/turtle-race

Make the existence of a turtle file imply a known-good metadata file.
Update backup to use __wt_schema_worker. Stop LSM drops during backups.
path variable no longer used, don't return without freeing the scratch buffer.
Merge branch 'develop' into hot-backup-schema
avoid spelling complaint
Delete test_illegal_objects, now that we're using schema_worker,
there's no special path for illegal objects and no reason to do
any special testing.
Re-work the code to build the target list, uncomment object checking,
this now works.
We have to write all of the names/value pairs out to the backup file,
not just the file: objects, don't discard the trailng ".wt" from the
file object name, whatever is in the metadata file is what we use.
Minor code shuffling/simplification, unused variable cleanups, comment fixing.
Update __wt_schema_worker so that it can operate on names.

It can now traverse either names, or files.
Merge pull request #558 from wiredtiger/hot-backup-schema

Update backup to use __wt_schema_worker. Stop LSM drops during backups.