(ITS#7453) Reset(MDB_NOSYNC/MDB_NOMETASYNC) fails

[h . b . furuseth]

Full_Name: Hallvard B Furuseth
Version: 2.4.33
OS: 
URL: 
Submission from: (NULL) (193.69.163.163)
Submitted by: hallvard


mdb_env_open() with MDB_NOSYNC or MDB_NOMETASYNC does not open a
sync descriptor, so resetting these flags does not work.  Fixing.