reduce logging levels for http errors (#112)

We see occasional HTTP errors when POSTing data to the backend. These are
often transient errors, and there is nothing that an end user can do about
them. Since we are ingesting spectatord logs, this results in creating
exception alerts, and we do not want this to happen. Thus, we turn down the
log levels for HTTP errors to info level, to prevent this scenario.

spectator/http_client.cc

@@ -251,10 +251,10 @@ auto HttpClient::perform(const char* method, const std::string& url,
   if (curl_res != CURLE_OK) {
     auto errbuff = curl.get_errbuf();
     if (errbuff[0] == '\0') {
-      logger->error("Failed to {} {}: {}",
+      logger->info("Failed to {} {}: {}",
                     method, url, curl_easy_strerror(curl_res));
     } else {
-      logger->error("Failed to {} {}: {} (errbuf={})",
+      logger->info("Failed to {} {}: {} (errbuf={})",
                     method, url, curl_easy_strerror(curl_res), errbuff);
     }
 
@@ -342,7 +342,7 @@ auto HttpClient::Post(const std::string& url, const char* content_type,
                                       &compressed_size, payload, size);
 
     if (compress_res != Z_OK) {
-      logger->error(
+      logger->info(
           "Failed to compress payload: {}, while posting to {} - uncompressed size: {}",
           compress_res, url, size);
       HttpResponse err{};