Use NOWAIT when including WAL in base backup

Avoids warning and waiting for the last segment to be
archived, which isn't necessary when we're including the
required WAL in the backup itself.

src/bin/pg_basebackup/pg_basebackup.c

@@ -777,11 +777,12 @@ BaseBackup()
 	 * Start the actual backup
 	 */
 	PQescapeStringConn(conn, escaped_label, label, sizeof(escaped_label), &i);
-	snprintf(current_path, sizeof(current_path), "BASE_BACKUP LABEL '%s' %s %s %s",
+	snprintf(current_path, sizeof(current_path), "BASE_BACKUP LABEL '%s' %s %s %s %s",
 			 escaped_label,
 			 showprogress ? "PROGRESS" : "",
 			 includewal ? "WAL" : "",
-			 fastcheckpoint ? "FAST" : "");
+			 fastcheckpoint ? "FAST" : "",
+	         includewal ? "NOWAIT" : "");
 
 	if (PQsendQuery(conn, current_path) == 0)
 	{