Fixes to streaming rollback processing

* Count separately fragments certified and fragments stored in
  streaming context. Storing the fragment may ultimately fail
  due to BF abort even if the fragment was succesfully certified.
  Therefore we need to have separate counter for certified fragments
  to determine if the transaction is streaming and seqnos of fragments
  which have been succesfully stored.
* Provider release is called only after succesful fragment certification
  and fragment store.
* Fixed handling of write sets with rollback flag set in apply_write_set()

include/wsrep/provider.hpp

@@ -16,6 +16,7 @@
 
 #include <string>
 #include <vector>
+#include <ostream>
 
 namespace wsrep
 {
@@ -128,6 +129,16 @@ namespace wsrep
         int flags_;
     };
 
+    static inline
+    std::ostream& operator<<(std::ostream& os, const wsrep::ws_meta& ws_meta)
+    {
+        os << "gtid: " << ws_meta.gtid()
+           << " server_id: " << ws_meta.server_id()
+           << " client_id: " << ws_meta.client_id()
+           << " trx_id: " << ws_meta.transaction_id()
+           << " flags: " << ws_meta.flags();
+        return os;
+    }
 
     // Abstract interface for provider implementations
     class provider