Fixed state destruction, which happened befor context_t destruction, which in turn calls logger.
Speed up server stop, by setting need-exit flag for all cache threads bfore joining them one after another.
v2.24.7.8
Do not destroy session in srw destructor, its lifetime is different. Do not destroy ctx in ~srw(), its lifetime is longer.
v2.24.7.9
Optimized dc.py. Added 'no-exit' parameter.
Merge pull request #122 from shaitan/master

Added no-exit dnet_recovery parameter. Optimized dc.py script.
recovery: added bytes statistics to recovery
recovery: misc formatting fixes
recovery: renamed collisions with python builtins
recovery: factor out common code to dnet_recovery
recovery: improved comments
recovery: added DurationTimer comment
recovery: spelling fix
recovery: dc: small fixes