log: Use LogWarning for non-critical logs

As per doc/developer-notes#logging, LogWarning should be used for severe
problems that do not warrant shutting down the node

src/logging.cpp

@@ -533,7 +533,7 @@ void BCLog::Logger::ShrinkDebugFile()
         // Restart the file with some of the end
         std::vector<char> vch(RECENT_DEBUG_HISTORY_SIZE, 0);
         if (fseek(file, -((long)vch.size()), SEEK_END)) {
-            LogPrintf("Failed to shrink debug log file: fseek(...) failed\n");
+            LogWarning("Failed to shrink debug log file: fseek(...) failed");
             fclose(file);
             return;
         }