runtests: slightly increase the longest log file displayed

The new limit provides enough space for a 64 KiB data block to be logged
in a trace file, plus a few lines at the start and end for context. This
happens to be the amount of data sent at a time in a PUT request.

tests/runtests.pl

@@ -2672,7 +2672,7 @@ sub displaylogcontent {
                     logmsg " $line\n";
                 }
                 $linecount++;
-                $truncate = $linecount > 1000;
+                $truncate = $linecount > 1200;
             }
         }
         close($single);