Fix various spelling errors

e.g.
- succesfully -> successfully
- preceeding -> preceding

include/wsrep/server_service.hpp

@@ -231,7 +231,7 @@ namespace wsrep
          * @param gtid A GTID denoting the current replication position
          * @param bypass Boolean bypass flag.
          *
-         * @return Zero if the SST transfer was succesfully started,
+         * @return Zero if the SST transfer was successfully started,
          *         non-zero otherwise.
          */
         virtual int start_sst(const std::string& sst_request,

include/wsrep/server_state.hpp

@@ -163,7 +163,7 @@ namespace wsrep
             s_connected,
             /** Server is receiving SST */
             s_joiner,
-            /** Server has received SST succesfully but has not synced
+            /** Server has received SST successfully but has not synced
               with rest of the cluster yet. */
             s_joined,
             /** Server is donating state snapshot transfer */

include/wsrep/transaction.hpp

@@ -93,7 +93,7 @@ namespace wsrep
         { return (ws_meta_.seqno().is_undefined() == false); }
 
         /**
-         * Return true if any fragments have been succesfully certified
+         * Return true if any fragments have been successfully certified
          * for the transaction.
          */
         bool is_streaming() const
@@ -104,7 +104,7 @@ namespace wsrep
         /**
          * Return number of fragments certified for current statement.
          *
-         * This counts fragments which have been succesfully certified
+         * This counts fragments which have been successfully certified
          * since the construction of object or last after_statement()
          * call.
          *