Log text of failed queries at log level ERROR

Previously query texts were always logged at log level DEBUG, but
that doesn't help much in a normal production environment when
trying to identify the cause of issues.

Also make various other minor improvements to query logging and
handling of database errors.

Implements GitHub #498.

HISTORY

@@ -1,4 +1,6 @@
 4.1.1   2018-??-??
+        logging: explicitly log the text of failed queries as ERRORs to
+          assist logfile analysis; GitHub #498
         repmgr: truncate version string, if necessary; GitHub #490 (Ian)
         repmgr: improve messages emitted during "standby promote" (Ian)
         repmgr: "standby clone" - don't copy external config files in --dry-run

doc/appendix-release-notes.sgml

@@ -17,7 +17,7 @@
 
   <sect1 id="release-4.1.1">
     <title>Release 4.1.1</title>
-    <para><emphasis>??? ??? ??, 2018</emphasis></para>
+    <para><emphasis>Wed September 5, 2018</emphasis></para>
     <para>
     </para>
 
@@ -33,6 +33,14 @@
             </para>
           </listitem>
 
+          <listitem>
+            <para>
+              Text of any failed queries will now be logged as <literal>ERROR</literal> to assist
+              logfile analysis at log levels higher than <literal>DEBUG</literal>.
+              (GitHub #498).
+            </para>
+          </listitem>
+
         </itemizedlist>
       </para>
    </sect2>

repmgr-action-cluster.c

@@ -1346,7 +1346,13 @@ do_cluster_cleanup(void)
 
 	entries_to_delete = get_number_of_monitoring_records_to_delete(primary_conn, runtime_options.keep_history);
 
-	if (entries_to_delete == 0)
+	if (entries_to_delete < 0)
+	{
+		log_error(_("unable to query number of monitoring records to clean up"));
+		PQfinish(primary_conn);
+		exit(ERR_DB_QUERY);
+	}
+	else if (entries_to_delete == 0)
 	{
 		log_info(_("no monitoring records to delete"));
 		PQfinish(primary_conn);

repmgr-action-primary.c

@@ -64,12 +64,10 @@ do_primary_register(void)
 			PQfinish(conn);
 			exit(ERR_BAD_CONFIG);
 		}
-		else
-		{
-			log_error(_("connection to node lost"));
-			PQfinish(conn);
-			exit(ERR_DB_CONN);
-		}
+
+		log_error(_("unable to determine server's recovery type"));
+		PQfinish(conn);
+		exit(ERR_DB_CONN);
 	}
 
 	log_verbose(LOG_INFO, _("server is not in recovery"));